diff --git a/README.ja-JP.md b/README.ja-JP.md
index 8c67db0..2e9d8c3 100644
--- a/README.ja-JP.md
+++ b/README.ja-JP.md
@@ -673,6 +673,11 @@ OCRは4層の優先度チェーンを使ってレビュールールを解決し
 | `llm.extra_headers` | string | カンマ区切りの `key=value` HTTPヘッダー |
 | `llm.model` | string | `claude-opus-4-6` |
 | `llm.use_anthropic` | boolean | `true` \| `false` |
+| `mcp_servers.<name>.command` | string | MCPサーバーを起動するコマンド |
+| `mcp_servers.<name>.args` | array | MCPサーバーのコマンドライン引数 |
+| `mcp_servers.<name>.env` | array | 環境変数（`KEY=VALUE`形式） |
+| `mcp_servers.<name>.tools` | array | 許可するツール名（空の場合はすべてのツール） |
+| `mcp_servers.<name>.setup` | string | サーバー起動前に実行するセットアップコマンド |
 | `language` | string | 任意の言語名、例：`English`、`Chinese`（デフォルト：`English`） |
 | `telemetry.enabled` | boolean | `true` \| `false` |
 | `telemetry.exporter` | string | `console` \| `otlp` |
@@ -681,6 +686,43 @@ OCRは4層の優先度チェーンを使ってレビュールールを解決し
 
 環境変数は設定ファイルより優先されます。
 
+### MCPサーバー
+
+Open Code Reviewは[Model Context Protocol (MCP)](https://modelcontextprotocol.io/)サーバーをサポートしており、レビューエージェントがstdioトランスポートを介してコードレビュー中に外部ツールを使用できます。
+
+CLIからMCPサーバーを設定します：
+
+```bash
+# MCPサーバーを追加
+ocr config set mcp_servers.<name>.command <command>
+ocr config set mcp_servers.<name>.args '["arg1","arg2"]'
+ocr config set mcp_servers.<name>.env '["KEY=VALUE"]'
+ocr config set mcp_servers.<name>.tools '["tool_name"]'
+ocr config set mcp_servers.<name>.setup '<setup command>'
+
+# MCPサーバーを削除
+ocr config unset mcp_servers.<name>
+```
+
+| フィールド | 必須 | 説明 |
+|-----------|------|------|
+| `command` | はい | MCPサーバーを起動する実行コマンド |
+| `args` | いいえ | サーバーに渡すコマンドライン引数 |
+| `env` | いいえ | 環境変数（`KEY=VALUE`形式） |
+| `tools` | いいえ | 許可するツール名。空の場合、サーバーのすべてのツールが利用可能 |
+| `setup` | いいえ | サーバー起動前に実行するシェルコマンド（例：インデックスの構築） |
+
+> **注意：** MCPツールの名前が組み込みツールと競合する場合、そのツールは警告付きでスキップされます。`setup`コマンドのタイムアウトは5分です。
+
+**例：[CodeGraph](https://github.com/nicholasgasior/codegraph)を追加してコード構造分析を強化**
+
+```bash
+ocr config set mcp_servers.codegraph.command codegraph
+ocr config set mcp_servers.codegraph.args '["serve","--mcp"]'
+ocr config set mcp_servers.codegraph.tools '["codegraph_explore"]'
+ocr config set mcp_servers.codegraph.setup 'codegraph init && codegraph index'
+```
+
 ### 環境変数
 
 | 変数 | 用途 |
diff --git a/README.ko-KR.md b/README.ko-KR.md
index 90b7225..06302f1 100644
--- a/README.ko-KR.md
+++ b/README.ko-KR.md
@@ -631,6 +631,11 @@ Config file: `~/.opencodereview/config.json`
 | `llm.extra_headers` | string | 쉼표로 구분된 `key=value` HTTP 헤더 |
 | `llm.model` | string | `claude-opus-4-6` |
 | `llm.use_anthropic` | boolean | `true` \| `false` |
+| `mcp_servers.<name>.command` | string | MCP 서버를 시작하는 명령어 |
+| `mcp_servers.<name>.args` | array | MCP 서버의 커맨드라인 인수 |
+| `mcp_servers.<name>.env` | array | 환경 변수 (`KEY=VALUE` 형식) |
+| `mcp_servers.<name>.tools` | array | 허용할 도구 이름 (비어 있으면 모든 도구 허용) |
+| `mcp_servers.<name>.setup` | string | 서버 시작 전에 실행할 설정 명령어 |
 | `language` | string | 임의의 언어 이름, 예: `English`, `Chinese` (기본값: `English`) |
 | `telemetry.enabled` | boolean | `true` \| `false` |
 | `telemetry.exporter` | string | `console` \| `otlp` |
@@ -639,6 +644,43 @@ Config file: `~/.opencodereview/config.json`
 
 환경 변수는 config file보다 우선합니다.
 
+### MCP Server
+
+Open Code Review는 [Model Context Protocol (MCP)](https://modelcontextprotocol.io/) 서버를 지원하여 리뷰 에이전트가 stdio 전송을 통해 코드 리뷰 중에 외부 도구를 사용할 수 있습니다.
+
+CLI로 MCP 서버를 설정합니다:
+
+```bash
+# MCP 서버 추가
+ocr config set mcp_servers.<name>.command <command>
+ocr config set mcp_servers.<name>.args '["arg1","arg2"]'
+ocr config set mcp_servers.<name>.env '["KEY=VALUE"]'
+ocr config set mcp_servers.<name>.tools '["tool_name"]'
+ocr config set mcp_servers.<name>.setup '<setup command>'
+
+# MCP 서버 삭제
+ocr config unset mcp_servers.<name>
+```
+
+| 필드 | 필수 | 설명 |
+|------|------|------|
+| `command` | 예 | MCP 서버를 시작하는 실행 명령어 |
+| `args` | 아니오 | 서버에 전달할 커맨드라인 인수 |
+| `env` | 아니오 | 환경 변수 (`KEY=VALUE` 형식) |
+| `tools` | 아니오 | 허용할 도구 이름. 비어 있으면 서버의 모든 도구 사용 가능 |
+| `setup` | 아니오 | 서버 시작 전에 실행할 셸 명령어 (예: 인덱스 빌드) |
+
+> **참고:** MCP 도구의 이름이 내장 도구와 충돌하면 경고와 함께 건너뜁니다. `setup` 명령어의 타임아웃은 5분입니다.
+
+**예시: [CodeGraph](https://github.com/nicholasgasior/codegraph)를 추가하여 코드 구조 분석 강화**
+
+```bash
+ocr config set mcp_servers.codegraph.command codegraph
+ocr config set mcp_servers.codegraph.args '["serve","--mcp"]'
+ocr config set mcp_servers.codegraph.tools '["codegraph_explore"]'
+ocr config set mcp_servers.codegraph.setup 'codegraph init && codegraph index'
+```
+
 ### Environment Variables
 
 | Variable | Purpose |
diff --git a/README.md b/README.md
index 4186fe0..8910699 100644
--- a/README.md
+++ b/README.md
@@ -678,6 +678,11 @@ Config file: `~/.opencodereview/config.json`
 | `llm.extra_headers` | string | Comma-separated `key=value` HTTP headers |
 | `llm.model` | string | `claude-opus-4-6` |
 | `llm.use_anthropic` | boolean | `true` \| `false` |
+| `mcp_servers.<name>.command` | string | Command to start the MCP server |
+| `mcp_servers.<name>.args` | array | Command-line arguments for the MCP server |
+| `mcp_servers.<name>.env` | array | Environment variables in `KEY=VALUE` format |
+| `mcp_servers.<name>.tools` | array | Allowed tool names (empty = all tools) |
+| `mcp_servers.<name>.setup` | string | Setup command to run before starting the server |
 | `language` | string | Any language name, e.g. `English`, `Chinese` (default: `English`) |
 | `telemetry.enabled` | boolean | `true` \| `false` |
 | `telemetry.exporter` | string | `console` \| `otlp` |
@@ -686,6 +691,43 @@ Config file: `~/.opencodereview/config.json`
 
 Environment variables take precedence over the config file.
 
+### MCP Server
+
+Open Code Review supports [Model Context Protocol (MCP)](https://modelcontextprotocol.io/) servers, allowing the review agent to use external tools during code review via the stdio transport.
+
+Configure MCP servers via the CLI:
+
+```bash
+# Add an MCP server
+ocr config set mcp_servers.<name>.command <command>
+ocr config set mcp_servers.<name>.args '["arg1","arg2"]'
+ocr config set mcp_servers.<name>.env '["KEY=VALUE"]'
+ocr config set mcp_servers.<name>.tools '["tool_name"]'
+ocr config set mcp_servers.<name>.setup '<setup command>'
+
+# Delete an MCP server
+ocr config unset mcp_servers.<name>
+```
+
+| Field | Required | Description |
+|-------|----------|-------------|
+| `command` | Yes | The executable command to start the MCP server |
+| `args` | No | Command-line arguments passed to the server |
+| `env` | No | Environment variables in `KEY=VALUE` format |
+| `tools` | No | Allowed tool names; if empty, all tools from the server are available |
+| `setup` | No | A shell command to run before starting the server (e.g. build an index) |
+
+> **Note:** If an MCP tool's name conflicts with a built-in tool, it will be skipped with a warning. The `setup` command has a 5-minute timeout.
+
+**Example: Add [CodeGraph](https://github.com/nicholasgasior/codegraph) for code structure analysis**
+
+```bash
+ocr config set mcp_servers.codegraph.command codegraph
+ocr config set mcp_servers.codegraph.args '["serve","--mcp"]'
+ocr config set mcp_servers.codegraph.tools '["codegraph_explore"]'
+ocr config set mcp_servers.codegraph.setup 'codegraph init && codegraph index'
+```
+
 ### Environment Variables
 
 | Variable | Purpose |
diff --git a/README.ru-RU.md b/README.ru-RU.md
index c22b8e0..7034883 100644
--- a/README.ru-RU.md
+++ b/README.ru-RU.md
@@ -675,6 +675,11 @@ OCR разрешает правила ревью по цепочке приор
 | `llm.extra_headers` | string | HTTP-заголовки `key=value` через запятую |
 | `llm.model` | string | `claude-opus-4-6` |
 | `llm.use_anthropic` | boolean | `true` \| `false` |
+| `mcp_servers.<name>.command` | string | Команда для запуска MCP-сервера |
+| `mcp_servers.<name>.args` | array | Аргументы командной строки для MCP-сервера |
+| `mcp_servers.<name>.env` | array | Переменные окружения в формате `KEY=VALUE` |
+| `mcp_servers.<name>.tools` | array | Разрешённые имена инструментов (пусто = все инструменты) |
+| `mcp_servers.<name>.setup` | string | Команда настройки перед запуском сервера |
 | `language` | string | Любое название языка, например `English`, `Chinese` (по умолчанию: `English`) |
 | `telemetry.enabled` | boolean | `true` \| `false` |
 | `telemetry.exporter` | string | `console` \| `otlp` |
@@ -683,6 +688,43 @@ OCR разрешает правила ревью по цепочке приор
 
 Переменные окружения имеют приоритет над файлом конфигурации.
 
+### MCP-сервер
+
+Open Code Review поддерживает серверы [Model Context Protocol (MCP)](https://modelcontextprotocol.io/), позволяя агенту ревью использовать внешние инструменты во время проверки кода через stdio-транспорт.
+
+Настройка MCP-серверов через CLI:
+
+```bash
+# Добавить MCP-сервер
+ocr config set mcp_servers.<name>.command <command>
+ocr config set mcp_servers.<name>.args '["arg1","arg2"]'
+ocr config set mcp_servers.<name>.env '["KEY=VALUE"]'
+ocr config set mcp_servers.<name>.tools '["tool_name"]'
+ocr config set mcp_servers.<name>.setup '<setup command>'
+
+# Удалить MCP-сервер
+ocr config unset mcp_servers.<name>
+```
+
+| Поле | Обязательно | Описание |
+|------|-------------|----------|
+| `command` | Да | Исполняемая команда для запуска MCP-сервера |
+| `args` | Нет | Аргументы командной строки для сервера |
+| `env` | Нет | Переменные окружения в формате `KEY=VALUE` |
+| `tools` | Нет | Разрешённые имена инструментов; если пусто — доступны все инструменты сервера |
+| `setup` | Нет | Shell-команда для выполнения перед запуском сервера (например, построение индекса) |
+
+> **Примечание:** Если имя MCP-инструмента конфликтует со встроенным инструментом, он будет пропущен с предупреждением. Таймаут команды `setup` составляет 5 минут.
+
+**Пример: добавление [CodeGraph](https://github.com/nicholasgasior/codegraph) для усиления анализа структуры кода**
+
+```bash
+ocr config set mcp_servers.codegraph.command codegraph
+ocr config set mcp_servers.codegraph.args '["serve","--mcp"]'
+ocr config set mcp_servers.codegraph.tools '["codegraph_explore"]'
+ocr config set mcp_servers.codegraph.setup 'codegraph init && codegraph index'
+```
+
 ### Переменные окружения
 
 | Переменная | Назначение |
diff --git a/README.zh-CN.md b/README.zh-CN.md
index 01df8a1..83524ea 100644
--- a/README.zh-CN.md
+++ b/README.zh-CN.md
@@ -663,6 +663,11 @@ OCR 通过四层优先级链解析评审规则。每层采用首次匹配原则
 | `llm.extra_headers` | string | 逗号分隔的 `key=value` HTTP 头 |
 | `llm.model` | string | `claude-opus-4-6` |
 | `llm.use_anthropic` | boolean | `true` \| `false` |
+| `mcp_servers.<name>.command` | string | 启动 MCP 服务器的命令 |
+| `mcp_servers.<name>.args` | array | MCP 服务器的命令行参数 |
+| `mcp_servers.<name>.env` | array | 环境变量，`KEY=VALUE` 格式 |
+| `mcp_servers.<name>.tools` | array | 允许使用的工具名称（为空则允许所有工具） |
+| `mcp_servers.<name>.setup` | string | 启动服务器前运行的初始化命令 |
 | `language` | string | 任意语言名称，例如 `English`、`Chinese`（默认：`English`） |
 | `telemetry.enabled` | boolean | `true` \| `false` |
 | `telemetry.exporter` | string | `console` \| `otlp` |
@@ -671,6 +676,43 @@ OCR 通过四层优先级链解析评审规则。每层采用首次匹配原则
 
 环境变量优先级高于配置文件。
 
+### MCP Server
+
+Open Code Review 支持 [Model Context Protocol (MCP)](https://modelcontextprotocol.io/) 服务器，允许评审 Agent 在代码评审过程中通过 stdio 传输协议调用外部工具。
+
+通过 CLI 配置 MCP 服务器：
+
+```bash
+# 添加 MCP 服务器
+ocr config set mcp_servers.<name>.command <command>
+ocr config set mcp_servers.<name>.args '["arg1","arg2"]'
+ocr config set mcp_servers.<name>.env '["KEY=VALUE"]'
+ocr config set mcp_servers.<name>.tools '["tool_name"]'
+ocr config set mcp_servers.<name>.setup '<setup command>'
+
+# 删除 MCP 服务器
+ocr config unset mcp_servers.<name>
+```
+
+| 字段 | 必填 | 说明 |
+|------|------|------|
+| `command` | 是 | 启动 MCP 服务器的可执行命令 |
+| `args` | 否 | 传递给服务器的命令行参数 |
+| `env` | 否 | 环境变量，`KEY=VALUE` 格式 |
+| `tools` | 否 | 允许使用的工具名称；为空则服务器的所有工具均可用 |
+| `setup` | 否 | 启动服务器前运行的 shell 命令（例如构建索引） |
+
+> **注意：** 如果 MCP 工具的名称与内置工具冲突，该工具将被跳过并输出警告。`setup` 命令的超时时间为 5 分钟。
+
+**示例：添加 [CodeGraph](https://github.com/nicholasgasior/codegraph) 增强代码结构分析能力**
+
+```bash
+ocr config set mcp_servers.codegraph.command codegraph
+ocr config set mcp_servers.codegraph.args '["serve","--mcp"]'
+ocr config set mcp_servers.codegraph.tools '["codegraph_explore"]'
+ocr config set mcp_servers.codegraph.setup 'codegraph init && codegraph index'
+```
+
 ### 环境变量
 
 | 变量 | 用途 |
diff --git a/cmd/opencodereview/config_cmd.go b/cmd/opencodereview/config_cmd.go
index 41cac15..64b511b 100644
--- a/cmd/opencodereview/config_cmd.go
+++ b/cmd/opencodereview/config_cmd.go
@@ -94,17 +94,23 @@ func runConfigSet(key, value string) error {
 
 func runConfigUnset(key string) error {
 	parts := strings.SplitN(key, ".", 2)
-	if len(parts) != 2 || parts[0] != "custom_providers" || parts[1] == "" {
-		return fmt.Errorf("unset only supports custom_providers.<name>")
+	if len(parts) != 2 || parts[1] == "" {
+		return fmt.Errorf("unset supports custom_providers.<name> and mcp_servers.<name>")
 	}
-	name := parts[1]
 
 	configPath, err := defaultConfigPath()
 	if err != nil {
 		return err
 	}
 
-	return unsetCustomProvider(configPath, name)
+	switch parts[0] {
+	case "custom_providers":
+		return unsetCustomProvider(configPath, parts[1])
+	case "mcp_servers":
+		return unsetMCPServer(configPath, parts[1])
+	default:
+		return fmt.Errorf("unset supports custom_providers.<name> and mcp_servers.<name>")
+	}
 }
 
 func unsetCustomProvider(configPath, name string) error {
@@ -130,6 +136,32 @@ func unsetCustomProvider(configPath, name string) error {
 	return nil
 }
 
+func unsetMCPServer(configPath, name string) error {
+	cfg, err := loadOrCreateConfig(configPath)
+	if err != nil {
+		return fmt.Errorf("load config: %w", err)
+	}
+
+	if cfg.MCPServers == nil {
+		return fmt.Errorf("MCP server %q not found", name)
+	}
+	if _, exists := cfg.MCPServers[name]; !exists {
+		return fmt.Errorf("MCP server %q not found", name)
+	}
+
+	delete(cfg.MCPServers, name)
+	if len(cfg.MCPServers) == 0 {
+		cfg.MCPServers = nil
+	}
+
+	if err := saveConfig(configPath, cfg); err != nil {
+		return err
+	}
+
+	fmt.Printf("Deleted MCP server %q.\n", name)
+	return nil
+}
+
 // deleteCustomProvider removes a custom provider from cfg in memory.
 // Returns true if the deleted provider was the active one.
 func deleteCustomProvider(cfg *Config, name string) (bool, error) {
@@ -166,15 +198,25 @@ type ProviderEntry struct {
 	ExtraHeaders map[string]string `json:"extra_headers,omitempty"`
 }
 
+// MCPServerConfig holds configuration for a single MCP server (stdio transport).
+type MCPServerConfig struct {
+	Command string   `json:"command"`
+	Args    []string `json:"args,omitempty"`
+	Env     []string `json:"env,omitempty"`
+	Tools   []string `json:"tools,omitempty"`
+	Setup   string   `json:"setup,omitempty"`
+}
+
 // Config represents the user-level configuration file (~/.opencodereview/config.json).
 type Config struct {
-	Provider        string                   `json:"provider,omitempty"`
-	Model           string                   `json:"model,omitempty"`
-	Providers       map[string]ProviderEntry `json:"providers,omitempty"`
-	CustomProviders map[string]ProviderEntry `json:"custom_providers,omitempty"`
-	Llm             LlmConfig                `json:"llm,omitempty"`
-	Language        string                   `json:"language,omitempty"`
-	Telemetry       *TelemetryConfig         `json:"telemetry,omitempty"`
+	Provider        string                     `json:"provider,omitempty"`
+	Model           string                     `json:"model,omitempty"`
+	Providers       map[string]ProviderEntry   `json:"providers,omitempty"`
+	CustomProviders map[string]ProviderEntry   `json:"custom_providers,omitempty"`
+	Llm             LlmConfig                  `json:"llm,omitempty"`
+	Language        string                     `json:"language,omitempty"`
+	Telemetry       *TelemetryConfig           `json:"telemetry,omitempty"`
+	MCPServers      map[string]MCPServerConfig `json:"mcp_servers,omitempty"`
 }
 
 type LlmConfig struct {
@@ -234,6 +276,9 @@ func setConfigValue(cfg *Config, key, value string) error {
 	if strings.HasPrefix(key, "custom_providers.") {
 		return setCustomProviderValue(cfg, key, value)
 	}
+	if strings.HasPrefix(key, "mcp_servers.") {
+		return setMCPServerValue(cfg, key, value)
+	}
 
 	switch key {
 	case "provider":
@@ -329,7 +374,7 @@ func setConfigValue(cfg *Config, key, value string) error {
 		}
 		cfg.Llm.ExtraBody = m
 	default:
-		return fmt.Errorf("unknown config key: %s\nSupported keys: provider, model, providers.<name>.<field>, custom_providers.<name>.<field>, llm.url, llm.auth_token, llm.auth_header, llm.model, llm.use_anthropic, llm.extra_body, llm.extra_headers, language, telemetry.enabled, telemetry.exporter, telemetry.otlp_endpoint, telemetry.content_logging\nProvider fields: api_key, url, protocol, model, models, auth_header, extra_body, extra_headers", key)
+		return fmt.Errorf("unknown config key: %s\nSupported keys: provider, model, providers.<name>.<field>, custom_providers.<name>.<field>, mcp_servers.<name>.<field>, llm.url, llm.auth_token, llm.auth_header, llm.model, llm.use_anthropic, llm.extra_body, llm.extra_headers, language, telemetry.enabled, telemetry.exporter, telemetry.otlp_endpoint, telemetry.content_logging\nProvider fields: api_key, url, protocol, model, models, auth_header, extra_body, extra_headers\nMCP server fields: command, args, env, tools, setup", key)
 	}
 	return nil
 }
@@ -491,6 +536,70 @@ func setCustomProviderField(cfg *Config, name, field, key, value string) error {
 	return nil
 }
 
+func setMCPServerValue(cfg *Config, key, value string) error {
+	parts := strings.SplitN(key, ".", 3)
+	if len(parts) != 3 || parts[1] == "" || parts[2] == "" {
+		return fmt.Errorf("invalid MCP server key %q: expected mcp_servers.<name>.<field>", key)
+	}
+	name, field := parts[1], parts[2]
+
+	if cfg.MCPServers == nil {
+		cfg.MCPServers = make(map[string]MCPServerConfig)
+	}
+	entry := cfg.MCPServers[name]
+
+	switch field {
+	case "command":
+		if value == "" {
+			return fmt.Errorf("MCP server command cannot be empty")
+		}
+		entry.Command = value
+	case "args":
+		var args []string
+		if err := json.Unmarshal([]byte(value), &args); err != nil {
+			return fmt.Errorf("invalid JSON array for %s: %w", key, err)
+		}
+		entry.Args = args
+	case "env":
+		var env []string
+		if err := json.Unmarshal([]byte(value), &env); err != nil {
+			return fmt.Errorf("invalid JSON array for %s: %w", key, err)
+		}
+		for _, e := range env {
+			idx := strings.Index(e, "=")
+			if idx <= 0 {
+				return fmt.Errorf("invalid env entry %q: must be in KEY=VALUE format", e)
+			}
+		}
+		entry.Env = env
+	case "tools":
+		var tools []string
+		if err := json.Unmarshal([]byte(value), &tools); err != nil {
+			return fmt.Errorf("invalid JSON array for %s: %w", key, err)
+		}
+		seen := make(map[string]struct{}, len(tools))
+		filtered := make([]string, 0, len(tools))
+		for _, t := range tools {
+			if t == "" {
+				return fmt.Errorf("tool names in %s must not be empty", key)
+			}
+			if _, dup := seen[t]; dup {
+				continue
+			}
+			seen[t] = struct{}{}
+			filtered = append(filtered, t)
+		}
+		entry.Tools = filtered
+	case "setup":
+		entry.Setup = value
+	default:
+		return fmt.Errorf("unknown MCP server field %q: supported fields are command, args, env, tools, setup", field)
+	}
+
+	cfg.MCPServers[name] = entry
+	return nil
+}
+
 func (c *Config) ensureTelemetry() {
 	if c.Telemetry == nil {
 		c.Telemetry = &TelemetryConfig{}
diff --git a/cmd/opencodereview/config_cmd_test.go b/cmd/opencodereview/config_cmd_test.go
index af1e43a..8c7de98 100644
--- a/cmd/opencodereview/config_cmd_test.go
+++ b/cmd/opencodereview/config_cmd_test.go
@@ -445,6 +445,236 @@ func TestMergeModelLists(t *testing.T) {
 	}
 }
 
+func TestSetMCPServerValue_Command(t *testing.T) {
+	cfg := &Config{}
+	if err := setMCPServerValue(cfg, "mcp_servers.my-server.command", "npx"); err != nil {
+		t.Fatalf("setMCPServerValue: %v", err)
+	}
+	if cfg.MCPServers["my-server"].Command != "npx" {
+		t.Errorf("Command = %q, want %q", cfg.MCPServers["my-server"].Command, "npx")
+	}
+}
+
+func TestSetMCPServerValue_CommandEmpty(t *testing.T) {
+	cfg := &Config{}
+	if err := setMCPServerValue(cfg, "mcp_servers.my-server.command", ""); err == nil {
+		t.Fatal("expected error for empty command")
+	}
+}
+
+func TestSetMCPServerValue_Args(t *testing.T) {
+	cfg := &Config{}
+	if err := setMCPServerValue(cfg, "mcp_servers.my-server.args", `["--port","8080"]`); err != nil {
+		t.Fatalf("setMCPServerValue: %v", err)
+	}
+	args := cfg.MCPServers["my-server"].Args
+	if len(args) != 2 || args[0] != "--port" || args[1] != "8080" {
+		t.Errorf("Args = %v", args)
+	}
+}
+
+func TestSetMCPServerValue_ArgsInvalidJSON(t *testing.T) {
+	cfg := &Config{}
+	if err := setMCPServerValue(cfg, "mcp_servers.my-server.args", "not-json"); err == nil {
+		t.Fatal("expected error for invalid JSON")
+	}
+}
+
+func TestSetMCPServerValue_Env(t *testing.T) {
+	cfg := &Config{}
+	if err := setMCPServerValue(cfg, "mcp_servers.my-server.env", `["FOO=bar","BAZ=qux"]`); err != nil {
+		t.Fatalf("setMCPServerValue: %v", err)
+	}
+	env := cfg.MCPServers["my-server"].Env
+	if len(env) != 2 || env[0] != "FOO=bar" {
+		t.Errorf("Env = %v", env)
+	}
+}
+
+func TestSetMCPServerValue_EnvInvalidJSON(t *testing.T) {
+	cfg := &Config{}
+	if err := setMCPServerValue(cfg, "mcp_servers.my-server.env", "not-json"); err == nil {
+		t.Fatal("expected error for invalid JSON")
+	}
+}
+
+func TestSetMCPServerValue_EnvInvalidFormat(t *testing.T) {
+	cfg := &Config{}
+	if err := setMCPServerValue(cfg, "mcp_servers.my-server.env", `["NOEQUALS"]`); err == nil {
+		t.Fatal("expected error for env entry without KEY=VALUE format")
+	}
+}
+
+func TestSetMCPServerValue_Tools(t *testing.T) {
+	cfg := &Config{}
+	if err := setMCPServerValue(cfg, "mcp_servers.my-server.tools", `["search","read","search"]`); err != nil {
+		t.Fatalf("setMCPServerValue: %v", err)
+	}
+	tools := cfg.MCPServers["my-server"].Tools
+	if len(tools) != 2 || tools[0] != "search" || tools[1] != "read" {
+		t.Errorf("Tools = %v (expected deduped)", tools)
+	}
+}
+
+func TestSetMCPServerValue_ToolsInvalidJSON(t *testing.T) {
+	cfg := &Config{}
+	if err := setMCPServerValue(cfg, "mcp_servers.my-server.tools", "not-json"); err == nil {
+		t.Fatal("expected error for invalid JSON")
+	}
+}
+
+func TestSetMCPServerValue_ToolsEmptyName(t *testing.T) {
+	cfg := &Config{}
+	if err := setMCPServerValue(cfg, "mcp_servers.my-server.tools", `["search",""]`); err == nil {
+		t.Fatal("expected error for empty tool name")
+	}
+}
+
+func TestSetMCPServerValue_Setup(t *testing.T) {
+	cfg := &Config{}
+	if err := setMCPServerValue(cfg, "mcp_servers.my-server.setup", "init-script.sh"); err != nil {
+		t.Fatalf("setMCPServerValue: %v", err)
+	}
+	if cfg.MCPServers["my-server"].Setup != "init-script.sh" {
+		t.Errorf("Setup = %q", cfg.MCPServers["my-server"].Setup)
+	}
+}
+
+func TestSetMCPServerValue_UnknownField(t *testing.T) {
+	cfg := &Config{}
+	if err := setMCPServerValue(cfg, "mcp_servers.my-server.unknown", "val"); err == nil {
+		t.Fatal("expected error for unknown field")
+	}
+}
+
+func TestSetMCPServerValue_InvalidKey(t *testing.T) {
+	cfg := &Config{}
+	tests := []string{
+		"mcp_servers",
+		"mcp_servers.",
+		"mcp_servers..command",
+		"mcp_servers.name",
+	}
+	for _, key := range tests {
+		if err := setMCPServerValue(cfg, key, "val"); err == nil {
+			t.Errorf("expected error for key %q", key)
+		}
+	}
+}
+
+func TestSetMCPServerValue_ExistingServer(t *testing.T) {
+	cfg := &Config{
+		MCPServers: map[string]MCPServerConfig{
+			"srv": {Command: "old-cmd"},
+		},
+	}
+	if err := setMCPServerValue(cfg, "mcp_servers.srv.command", "new-cmd"); err != nil {
+		t.Fatalf("setMCPServerValue: %v", err)
+	}
+	if cfg.MCPServers["srv"].Command != "new-cmd" {
+		t.Errorf("Command = %q, want %q", cfg.MCPServers["srv"].Command, "new-cmd")
+	}
+}
+
+func TestUnsetMCPServer(t *testing.T) {
+	dir := t.TempDir()
+	configPath := dir + "/config.json"
+
+	cfg := &Config{
+		MCPServers: map[string]MCPServerConfig{
+			"srv1": {Command: "cmd1"},
+			"srv2": {Command: "cmd2"},
+		},
+	}
+	if err := saveConfig(configPath, cfg); err != nil {
+		t.Fatalf("saveConfig: %v", err)
+	}
+
+	if err := unsetMCPServer(configPath, "srv1"); err != nil {
+		t.Fatalf("unsetMCPServer: %v", err)
+	}
+
+	cfg, err := loadOrCreateConfig(configPath)
+	if err != nil {
+		t.Fatalf("reload: %v", err)
+	}
+	if _, exists := cfg.MCPServers["srv1"]; exists {
+		t.Error("srv1 should have been deleted")
+	}
+	if _, exists := cfg.MCPServers["srv2"]; !exists {
+		t.Error("srv2 should still exist")
+	}
+}
+
+func TestUnsetMCPServer_LastEntry(t *testing.T) {
+	dir := t.TempDir()
+	configPath := dir + "/config.json"
+
+	cfg := &Config{
+		MCPServers: map[string]MCPServerConfig{
+			"only": {Command: "cmd"},
+		},
+	}
+	if err := saveConfig(configPath, cfg); err != nil {
+		t.Fatalf("saveConfig: %v", err)
+	}
+
+	if err := unsetMCPServer(configPath, "only"); err != nil {
+		t.Fatalf("unsetMCPServer: %v", err)
+	}
+
+	cfg, err := loadOrCreateConfig(configPath)
+	if err != nil {
+		t.Fatalf("reload: %v", err)
+	}
+	if cfg.MCPServers != nil {
+		t.Errorf("MCPServers should be nil after deleting last entry, got %v", cfg.MCPServers)
+	}
+}
+
+func TestUnsetMCPServer_NotFound(t *testing.T) {
+	dir := t.TempDir()
+	configPath := dir + "/config.json"
+
+	cfg := &Config{}
+	if err := saveConfig(configPath, cfg); err != nil {
+		t.Fatalf("saveConfig: %v", err)
+	}
+
+	if err := unsetMCPServer(configPath, "nonexistent"); err == nil {
+		t.Fatal("expected error for nil MCPServers")
+	}
+
+	cfg = &Config{
+		MCPServers: map[string]MCPServerConfig{
+			"other": {Command: "cmd"},
+		},
+	}
+	if err := saveConfig(configPath, cfg); err != nil {
+		t.Fatalf("saveConfig: %v", err)
+	}
+
+	if err := unsetMCPServer(configPath, "nonexistent"); err == nil {
+		t.Fatal("expected error for missing server")
+	}
+}
+
+func TestRunConfigUnset_UnknownPrefix(t *testing.T) {
+	if err := runConfigUnset("providers.anthropic"); err == nil {
+		t.Fatal("expected error for unsupported prefix")
+	}
+}
+
+func TestSetConfigValueMCPServer(t *testing.T) {
+	cfg := &Config{}
+	if err := setConfigValue(cfg, "mcp_servers.my-server.command", "npx"); err != nil {
+		t.Fatalf("setConfigValue: %v", err)
+	}
+	if cfg.MCPServers["my-server"].Command != "npx" {
+		t.Errorf("Command = %q", cfg.MCPServers["my-server"].Command)
+	}
+}
+
 func TestEnsureTelemetry(t *testing.T) {
 	cfg := &Config{}
 	if cfg.Telemetry != nil {
diff --git a/cmd/opencodereview/flags.go b/cmd/opencodereview/flags.go
index 4432ceb..ccda515 100644
--- a/cmd/opencodereview/flags.go
+++ b/cmd/opencodereview/flags.go
@@ -275,6 +275,7 @@ func printConfigUsage() {
 Usage:
   ocr config set <key> <value>
   ocr config unset custom_providers.<name>  Delete a custom provider
+  ocr config unset mcp_servers.<name>       Delete an MCP server
   ocr config provider                       Interactive provider setup
   ocr config model                          Interactive model selection
 
@@ -301,6 +302,14 @@ Examples:
   # Delete a custom provider
   ocr config unset custom_providers.my-gateway
 
+  # MCP server configuration (stdio transport)
+  ocr config set mcp_servers.codegraph.command npx
+  ocr config set mcp_servers.codegraph.args '["-y","@anthropic/codegraph-mcp"]'
+  ocr config set mcp_servers.codegraph.env '["CODEGRAPH_TOKEN=xxx"]'
+
+  # Delete an MCP server
+  ocr config unset mcp_servers.codegraph
+
   # Legacy endpoint configuration
   ocr config set llm.url https://xx/v1/openai/chat/completions
   ocr config set llm.auth_token xxxxxxxxxx
@@ -310,6 +319,7 @@ Examples:
   ocr config set language English
   ocr config set telemetry.enabled true
 
-Supported keys: provider, model, providers.<name>.<field>, custom_providers.<name>.<field>, llm.url, llm.auth_token, llm.auth_header, llm.model, llm.use_anthropic, llm.extra_body, language, telemetry.enabled, telemetry.exporter, telemetry.otlp_endpoint, telemetry.content_logging
-Provider fields: api_key, url, protocol, model, models, auth_header, extra_body`)
+Supported keys: provider, model, providers.<name>.<field>, custom_providers.<name>.<field>, mcp_servers.<name>.<field>, llm.url, llm.auth_token, llm.auth_header, llm.model, llm.use_anthropic, llm.extra_body, llm.extra_headers, language, telemetry.enabled, telemetry.exporter, telemetry.otlp_endpoint, telemetry.content_logging
+Provider fields: api_key, url, protocol, model, models, auth_header, extra_body, extra_headers
+MCP server fields: command, args, env, tools, setup`)
 }
diff --git a/cmd/opencodereview/procattr_unix.go b/cmd/opencodereview/procattr_unix.go
new file mode 100644
index 0000000..6861ead
--- /dev/null
+++ b/cmd/opencodereview/procattr_unix.go
@@ -0,0 +1,18 @@
+//go:build !windows
+
+package main
+
+import (
+	"os/exec"
+	"syscall"
+)
+
+func configureProcessGroup(cmd *exec.Cmd) {
+	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+	cmd.Cancel = func() error {
+		if cmd.Process == nil {
+			return nil
+		}
+		return syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
+	}
+}
diff --git a/cmd/opencodereview/procattr_windows.go b/cmd/opencodereview/procattr_windows.go
new file mode 100644
index 0000000..4b947be
--- /dev/null
+++ b/cmd/opencodereview/procattr_windows.go
@@ -0,0 +1,12 @@
+//go:build windows
+
+package main
+
+import "os/exec"
+
+func configureProcessGroup(cmd *exec.Cmd) {
+	// On Windows, exec.CommandContext sends os.Kill which terminates the
+	// direct child. Grandchild processes (e.g. from sh -c) may survive.
+	// Full process-tree cleanup would need Windows Job Objects, but sh -c
+	// is rare on Windows so this is an acceptable limitation.
+}
diff --git a/cmd/opencodereview/review_cmd.go b/cmd/opencodereview/review_cmd.go
index 91a7491..d76951b 100644
--- a/cmd/opencodereview/review_cmd.go
+++ b/cmd/opencodereview/review_cmd.go
@@ -5,10 +5,12 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"sort"
 	"strings"
 	"time"
 
 	"github.com/open-code-review/open-code-review/internal/agent"
+	"github.com/open-code-review/open-code-review/internal/mcp"
 	"github.com/open-code-review/open-code-review/internal/telemetry"
 	"github.com/open-code-review/open-code-review/internal/tool"
 )
@@ -61,6 +63,19 @@ func runReview(args []string) error {
 	}
 	tools := buildToolRegistry(rt.Collector, fileReader)
 
+	mcpClients := initMCPClients(context.Background(), rt.AppCfg, tools, cc.RepoDir, Version)
+	defer func() {
+		for _, mc := range mcpClients {
+			if err := mc.Close(); err != nil {
+				fmt.Fprintf(os.Stderr, "[ocr] WARNING: failed to close MCP server %q: %v\n", mc.Name(), err)
+			}
+		}
+	}()
+
+	mcpToolDefs := mcp.CollectToolDefs(mcpClients, tools)
+	rt.PlanToolDefs = append(rt.PlanToolDefs, mcpToolDefs...)
+	rt.MainToolDefs = append(rt.MainToolDefs, mcpToolDefs...)
+
 	ag := agent.New(agent.Args{
 		RepoDir:               cc.RepoDir,
 		From:                  opts.from,
@@ -180,6 +195,58 @@ func runPreview(cc *commonContext, opts reviewOptions) error {
 	return nil
 }
 
+func initMCPClients(ctx context.Context, cfg *Config, tools *tool.Registry, repoDir, version string) []*mcp.Client {
+	if cfg == nil || len(cfg.MCPServers) == 0 {
+		return nil
+	}
+
+	mcpNames := make([]string, 0, len(cfg.MCPServers))
+	for name := range cfg.MCPServers {
+		mcpNames = append(mcpNames, name)
+	}
+	sort.Strings(mcpNames)
+
+	var clients []*mcp.Client
+	for _, name := range mcpNames {
+		serverCfg := cfg.MCPServers[name]
+		if serverCfg.Command == "" {
+			fmt.Fprintf(os.Stderr, "[ocr] WARNING: MCP server %q has no command configured, skipping\n", name)
+			continue
+		}
+		if serverCfg.Setup != "" {
+			fmt.Fprintf(os.Stderr, "[ocr] Running setup for MCP server %q: %s\n", name, serverCfg.Setup)
+			setupCtx, setupCancel := context.WithTimeout(ctx, 5*time.Minute)
+			setupCmd := shellCommand(setupCtx, serverCfg.Setup)
+			setupCmd.Dir = repoDir
+			configureProcessGroup(setupCmd)
+			output, err := setupCmd.CombinedOutput()
+			setupCancel()
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "[ocr] ERROR: MCP server %q setup command failed.\n", name)
+				fmt.Fprintf(os.Stderr, "[ocr]   Command: %s\n", serverCfg.Setup)
+				fmt.Fprintf(os.Stderr, "[ocr]   Working directory: %s\n", repoDir)
+				fmt.Fprintf(os.Stderr, "[ocr]   Error: %v\n", err)
+				if len(output) > 0 {
+					fmt.Fprintf(os.Stderr, "[ocr]   Output:\n%s\n", string(output))
+				}
+				fmt.Fprintf(os.Stderr, "[ocr]   Skipping MCP server %q — review will proceed without it.\n", name)
+				continue
+			}
+		}
+
+		initCtx, initCancel := context.WithTimeout(ctx, 30*time.Second)
+		mc, err := mcp.NewClient(initCtx, name, serverCfg.Command, serverCfg.Args, serverCfg.Env, repoDir, version)
+		initCancel()
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "[ocr] WARNING: failed to start MCP server %q: %v\n", name, err)
+			continue
+		}
+		clients = append(clients, mc)
+		mcp.RegisterAll(tools, mc, serverCfg.Tools)
+	}
+	return clients
+}
+
 func buildToolRegistry(collector *tool.CommentCollector, fr *tool.FileReader) *tool.Registry {
 	reg := tool.NewRegistry()
 	reg.Register(tool.NewFileRead(fr))
diff --git a/cmd/opencodereview/shell_unix.go b/cmd/opencodereview/shell_unix.go
new file mode 100644
index 0000000..a66ce86
--- /dev/null
+++ b/cmd/opencodereview/shell_unix.go
@@ -0,0 +1,12 @@
+//go:build !windows
+
+package main
+
+import (
+	"context"
+	"os/exec"
+)
+
+func shellCommand(ctx context.Context, script string) *exec.Cmd {
+	return exec.CommandContext(ctx, "sh", "-c", script)
+}
diff --git a/cmd/opencodereview/shell_windows.go b/cmd/opencodereview/shell_windows.go
new file mode 100644
index 0000000..bfb0311
--- /dev/null
+++ b/cmd/opencodereview/shell_windows.go
@@ -0,0 +1,12 @@
+//go:build windows
+
+package main
+
+import (
+	"context"
+	"os/exec"
+)
+
+func shellCommand(ctx context.Context, script string) *exec.Cmd {
+	return exec.CommandContext(ctx, "cmd", "/c", script)
+}
diff --git a/go.mod b/go.mod
index 3f48112..84dc3a3 100644
--- a/go.mod
+++ b/go.mod
@@ -1,6 +1,6 @@
 module github.com/open-code-review/open-code-review
 
-go 1.25.0
+go 1.25.5
 
 require (
 	charm.land/bubbles/v2 v2.1.0
@@ -8,6 +8,7 @@ require (
 	charm.land/lipgloss/v2 v2.0.4
 	github.com/anthropics/anthropic-sdk-go v1.52.0
 	github.com/bmatcuk/doublestar/v4 v4.10.0
+	github.com/modelcontextprotocol/go-sdk v1.6.1
 	github.com/openai/openai-go/v3 v3.41.0
 	github.com/pkoukk/tiktoken-go v0.1.8
 	go.opentelemetry.io/otel v1.44.0
@@ -35,9 +36,10 @@ require (
 	github.com/charmbracelet/x/windows v0.2.2 // indirect
 	github.com/clipperhouse/displaywidth v0.11.0 // indirect
 	github.com/clipperhouse/uax29/v2 v2.7.0 // indirect
-	github.com/dlclark/regexp2 v1.10.0 // indirect
+	github.com/dlclark/regexp2 v1.11.0 // indirect
 	github.com/go-logr/logr v1.4.3 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
+	github.com/google/jsonschema-go v0.4.3 // indirect
 	github.com/google/uuid v1.6.0 // indirect
 	github.com/grpc-ecosystem/grpc-gateway/v2 v2.29.0 // indirect
 	github.com/invopop/jsonschema v0.14.0 // indirect
@@ -46,17 +48,21 @@ require (
 	github.com/muesli/cancelreader v0.2.2 // indirect
 	github.com/pb33f/ordered-map/v2 v2.3.1 // indirect
 	github.com/rivo/uniseg v0.4.7 // indirect
+	github.com/segmentio/asm v1.1.3 // indirect
+	github.com/segmentio/encoding v0.5.4 // indirect
 	github.com/standard-webhooks/standard-webhooks/libraries v0.0.1 // indirect
 	github.com/tidwall/gjson v1.18.0 // indirect
 	github.com/tidwall/match v1.1.1 // indirect
 	github.com/tidwall/pretty v1.2.1 // indirect
 	github.com/tidwall/sjson v1.2.5 // indirect
 	github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e // indirect
+	github.com/yosida95/uritemplate/v3 v3.0.2 // indirect
 	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.44.0 // indirect
 	go.opentelemetry.io/proto/otlp v1.10.0 // indirect
 	go.yaml.in/yaml/v4 v4.0.0-rc.2 // indirect
 	golang.org/x/net v0.55.0 // indirect
+	golang.org/x/oauth2 v0.36.0 // indirect
 	golang.org/x/sync v0.20.0 // indirect
 	golang.org/x/sys v0.45.0 // indirect
 	golang.org/x/text v0.37.0 // indirect
diff --git a/go.sum b/go.sum
index 5085065..bb44b6b 100644
--- a/go.sum
+++ b/go.sum
@@ -40,8 +40,8 @@ github.com/clipperhouse/uax29/v2 v2.7.0 h1:+gs4oBZ2gPfVrKPthwbMzWZDaAFPGYK72F0NJ
 github.com/clipperhouse/uax29/v2 v2.7.0/go.mod h1:EFJ2TJMRUaplDxHKj1qAEhCtQPW2tJSwu5BF98AuoVM=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/dlclark/regexp2 v1.10.0 h1:+/GIL799phkJqYW+3YbOd8LCcbHzT0Pbo8zl70MHsq0=
-github.com/dlclark/regexp2 v1.10.0/go.mod h1:DHkYz0B9wPfa6wondMfaivmHpzrQ3v9q8cnmRbL6yW8=
+github.com/dlclark/regexp2 v1.11.0 h1:G/nrcoOa7ZXlpoa/91N3X7mM3r8eIlMBBJZvsz/mxKI=
+github.com/dlclark/regexp2 v1.11.0/go.mod h1:DHkYz0B9wPfa6wondMfaivmHpzrQ3v9q8cnmRbL6yW8=
 github.com/dnaeon/go-vcr v1.2.0 h1:zHCHvJYTMh1N7xnV7zf1m1GPBF9Ad0Jk/whtQ1663qI=
 github.com/dnaeon/go-vcr v1.2.0/go.mod h1:R4UdLID7HZT3taECzJs4YgbbH6PIGXB6W/sc5OLb6RQ=
 github.com/go-logr/logr v1.2.2/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
@@ -49,10 +49,14 @@ github.com/go-logr/logr v1.4.3 h1:CjnDlHq8ikf6E492q6eKboGOC0T8CDaOvkHCIg8idEI=
 github.com/go-logr/logr v1.4.3/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
 github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
 github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
+github.com/golang-jwt/jwt/v5 v5.3.1 h1:kYf81DTWFe7t+1VvL7eS+jKFVWaUnK9cB1qbwn63YCY=
+github.com/golang-jwt/jwt/v5 v5.3.1/go.mod h1:fxCRLWMO43lRc8nhHWY6LGqRcf+1gQWArsqaEUEa5bE=
 github.com/golang/protobuf v1.5.4 h1:i7eJL8qZTpSEXOPTxNKhASYpMn+8e5Q6AdndVa1dWek=
 github.com/golang/protobuf v1.5.4/go.mod h1:lnTiLA8Wa4RWRcIUkrtSVa5nRhsEGBg48fD6rSs7xps=
 github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
 github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
+github.com/google/jsonschema-go v0.4.3 h1:/DBOLZTfDow7pe2GmaJNhltueGTtDKICi8V8p+DQPd0=
+github.com/google/jsonschema-go v0.4.3/go.mod h1:r5quNTdLOYEz95Ru18zA0ydNbBuYoo9tgaYcxEYhJVE=
 github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/grpc-ecosystem/grpc-gateway/v2 v2.29.0 h1:5VipnvEpbqr2gA2VbM+nYVbkIF28c5ZQfqCBQ5g2xfk=
@@ -63,6 +67,8 @@ github.com/lucasb-eyer/go-colorful v1.4.0 h1:UtrWVfLdarDgc44HcS7pYloGHJUjHV/4FwW
 github.com/lucasb-eyer/go-colorful v1.4.0/go.mod h1:R4dSotOR9KMtayYi1e77YzuveK+i7ruzyGqttikkLy0=
 github.com/mattn/go-runewidth v0.0.23 h1:7ykA0T0jkPpzSvMS5i9uoNn2Xy3R383f9HDx3RybWcw=
 github.com/mattn/go-runewidth v0.0.23/go.mod h1:XBkDxAl56ILZc9knddidhrOlY5R/pDhgLpndooCuJAs=
+github.com/modelcontextprotocol/go-sdk v1.6.1 h1:0zOSupjKUxPKSocPT1Wtago+mUHU2/uZ4xSOY0FGReU=
+github.com/modelcontextprotocol/go-sdk v1.6.1/go.mod h1:kzm3kzFL1/+AziGOE0nUs3gvPoNxMCvkxokMkuFapXQ=
 github.com/muesli/cancelreader v0.2.2 h1:3I4Kt4BQjOR54NavqnDogx/MIoWBFa0StPA8ELUXHmA=
 github.com/muesli/cancelreader v0.2.2/go.mod h1:3XuTXfFS2VjM+HTLZY9Ak0l6eUKfijIfMUZ4EgX0QYo=
 github.com/openai/openai-go/v3 v3.41.0 h1:9GkxcN02U5NG0WGdQjZ0cTSu/pMXEyzL2LfF0ruZCck=
@@ -75,6 +81,10 @@ github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZb
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/rivo/uniseg v0.4.7 h1:WUdvkW8uEhrYfLC4ZzdpI2ztxP1I582+49Oc5Mq64VQ=
 github.com/rivo/uniseg v0.4.7/go.mod h1:FN3SvrM+Zdj16jyLfmOkMNblXMcoc8DfTHruCPUcx88=
+github.com/segmentio/asm v1.1.3 h1:WM03sfUOENvvKexOLp+pCqgb/WDjsi7EK8gIsICtzhc=
+github.com/segmentio/asm v1.1.3/go.mod h1:Ld3L4ZXGNcSLRg4JBsZ3//1+f/TjYl0Mzen/DQy1EJg=
+github.com/segmentio/encoding v0.5.4 h1:OW1VRern8Nw6ITAtwSZ7Idrl3MXCFwXHPgqESYfvNt0=
+github.com/segmentio/encoding v0.5.4/go.mod h1:HS1ZKa3kSN32ZHVZ7ZLPLXWvOVIiZtyJnO1gPH1sKt0=
 github.com/standard-webhooks/standard-webhooks/libraries v0.0.1 h1:uOfcYT+3QungH6tIGSVCR/Y3KJmgJiHcojJbMTPDZAI=
 github.com/standard-webhooks/standard-webhooks/libraries v0.0.1/go.mod h1:L1MQhA6x4dn9r007T033lsaZMv9EmBAdXyU/+EF40fo=
 github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
@@ -91,6 +101,8 @@ github.com/tidwall/sjson v1.2.5 h1:kLy8mja+1c9jlljvWTlSazM7cKDRfJuR/bOJhcY5NcY=
 github.com/tidwall/sjson v1.2.5/go.mod h1:Fvgq9kS/6ociJEDnK0Fk1cpYF4FIW6ZF7LAe+6jwd28=
 github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e h1:JVG44RsyaB9T2KIHavMF/ppJZNG9ZpyihvCd0w101no=
 github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e/go.mod h1:RbqR21r5mrJuqunuUZ/Dhy/avygyECGrLceyNeo4LiM=
+github.com/yosida95/uritemplate/v3 v3.0.2 h1:Ed3Oyj9yrmi9087+NczuL5BwkIc4wvTb5zIM+UJPGz4=
+github.com/yosida95/uritemplate/v3 v3.0.2/go.mod h1:ILOh0sOhIJR3+L/8afwt/kE++YT040gmv5BQTMR2HP4=
 go.opentelemetry.io/auto/sdk v1.2.1 h1:jXsnJ4Lmnqd11kwkBV2LgLoFMZKizbCi5fNZ/ipaZ64=
 go.opentelemetry.io/auto/sdk v1.2.1/go.mod h1:KRTj+aOaElaLi+wW1kO/DZRXwkF4C5xPbEe3ZiIhN7Y=
 go.opentelemetry.io/otel v1.44.0 h1:JjwHmHpA4iZ3wBxluu2fbbE7j4kqlE8jXyAyPXH7HqU=
@@ -125,12 +137,16 @@ golang.org/x/exp v0.0.0-20231006140011-7918f672742d h1:jtJma62tbqLibJ5sFQz8bKtEM
 golang.org/x/exp v0.0.0-20231006140011-7918f672742d/go.mod h1:ldy0pHrwJyGW56pPQzzkH36rKxoZW1tw7ZJpeKx+hdo=
 golang.org/x/net v0.55.0 h1:bcvxaJn3e1U6InsFWt1JUq1aSjnRxLzT2rtD2KfkDF8=
 golang.org/x/net v0.55.0/go.mod h1:L5U2KuzuOe1lY7Z+aWVIKK6qEeJXnXV9yzGA+WCHJww=
+golang.org/x/oauth2 v0.36.0 h1:peZ/1z27fi9hUOFCAZaHyrpWG5lwe0RJEEEeH0ThlIs=
+golang.org/x/oauth2 v0.36.0/go.mod h1:YDBUJMTkDnJS+A4BP4eZBjCqtokkg1hODuPjwiGPO7Q=
 golang.org/x/sync v0.20.0 h1:e0PTpb7pjO8GAtTs2dQ6jYa5BWYlMuX047Dco/pItO4=
 golang.org/x/sync v0.20.0/go.mod h1:9xrNwdLfx4jkKbNva9FpL6vEN7evnE43NNNJQ2LF3+0=
 golang.org/x/sys v0.45.0 h1:dO4czNzziLiiXplLQgBCEpCvXQ3dnkn0SdaZSYdQ+FY=
 golang.org/x/sys v0.45.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
 golang.org/x/text v0.37.0 h1:Cqjiwd9eSg8e0QAkyCaQTNHFIIzWtidPahFWR83rTrc=
 golang.org/x/text v0.37.0/go.mod h1:a5sjxXGs9hsn/AJVwuElvCAo9v8QYLzvavO5z2PiM38=
+golang.org/x/tools v0.44.0 h1:UP4ajHPIcuMjT1GqzDWRlalUEoY+uzoZKnhOjbIPD2c=
+golang.org/x/tools v0.44.0/go.mod h1:KA0AfVErSdxRZIsOVipbv3rQhVXTnlU6UhKxHd1seDI=
 gonum.org/v1/gonum v0.17.0 h1:VbpOemQlsSMrYmn7T2OUvQ4dqxQXU+ouZFQsZOx50z4=
 gonum.org/v1/gonum v0.17.0/go.mod h1:El3tOrEuMpv2UdMrbNlKEh9vd86bmQ6vqIcDwxEOc1E=
 google.golang.org/genproto/googleapis/api v0.0.0-20260526163538-3dc84a4a5aaa h1:Kjn0N0tCrDgiAFW+lGO4JZ3ck44CehvJQMAwj9QF0G8=
diff --git a/internal/llmloop/loop.go b/internal/llmloop/loop.go
index 5239a04..d206a78 100644
--- a/internal/llmloop/loop.go
+++ b/internal/llmloop/loop.go
@@ -260,8 +260,32 @@ func (r *Runner) RunPerFile(ctx context.Context, messages []llm.Message, newPath
 // resolution / re-location.
 func (r *Runner) executeToolCall(ctx context.Context, newPath string, call llm.ToolCall, rec *session.TaskRecord) tool.TaskCheckpoint {
 	t := tool.OfName(call.Function.Name)
+
 	if !t.IsKnown() {
-		return tool.Of(tool.NotAvailableMsg)
+		p, ok := r.deps.Tools.Get(call.Function.Name)
+		if !ok {
+			return tool.Of(tool.NotAvailableMsg)
+		}
+		r.recordToolCall(call.Function.Name)
+		var dynArgs map[string]any
+		if err := json.Unmarshal([]byte(call.Function.Arguments), &dynArgs); err != nil {
+			return tool.Of(fmt.Sprintf("Error parsing tool arguments for %s: %v", call.Function.Name, err))
+		}
+		telemetry.PrintToolCallStarted(call.Function.Name, dynArgs)
+		startTime := time.Now()
+		result, err := p.Execute(ctx, dynArgs)
+		dur := time.Since(startTime)
+		if err != nil {
+			telemetry.RecordToolCall(ctx, call.Function.Name, dur, false)
+			telemetry.PrintToolCallError(call.Function.Name, err)
+			return tool.Of(fmt.Sprintf("Error executing tool %s: %v", call.Function.Name, err))
+		}
+		telemetry.RecordToolCall(ctx, call.Function.Name, dur, true)
+		telemetry.PrintToolCallFinished(call.Function.Name, dur)
+		if rec != nil {
+			rec.AddToolResult(call.Function.Name, call.Function.Arguments, result)
+		}
+		return tool.Of(result)
 	}
 
 	if t == tool.TaskDone {
diff --git a/internal/mcp/client.go b/internal/mcp/client.go
new file mode 100644
index 0000000..b06d7cd
--- /dev/null
+++ b/internal/mcp/client.go
@@ -0,0 +1,103 @@
+package mcp
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+
+	"github.com/modelcontextprotocol/go-sdk/mcp"
+)
+
+// Client wraps a single MCP server connection via stdio transport.
+type Client struct {
+	name    string
+	session *mcp.ClientSession
+	tools   []*mcp.Tool
+}
+
+// NewClient starts an MCP server subprocess, initializes the connection,
+// and caches the list of available tools. The context governs the
+// initialization timeout (Connect + ListTools), NOT the subprocess
+// lifetime — the subprocess stays alive until Close is called.
+// When dir is non-empty, the subprocess runs with that working directory.
+func NewClient(ctx context.Context, name, command string, args, env []string, dir, version string) (*Client, error) {
+	cmd := exec.Command(command, args...)
+	cmd.Env = append(os.Environ(), env...)
+	if dir != "" {
+		cmd.Dir = dir
+	}
+
+	client := mcp.NewClient(
+		&mcp.Implementation{Name: "open-code-review", Version: version},
+		nil,
+	)
+
+	transport := &mcp.CommandTransport{Command: cmd}
+	session, err := client.Connect(ctx, transport, nil)
+	if err != nil {
+		return nil, fmt.Errorf("connect to MCP server %q: %w", name, err)
+	}
+
+	var success bool
+	defer func() {
+		if !success {
+			session.Close()
+		}
+	}()
+
+	toolsResult, err := session.ListTools(ctx, nil)
+	if err != nil {
+		return nil, fmt.Errorf("list tools from MCP server %q: %w", name, err)
+	}
+
+	success = true
+	return &Client{
+		name:    name,
+		session: session,
+		tools:   toolsResult.Tools,
+	}, nil
+}
+
+func (c *Client) Name() string       { return c.name }
+func (c *Client) Tools() []*mcp.Tool { return c.tools }
+
+// CallTool invokes a tool on the MCP server and returns the text result.
+func (c *Client) CallTool(ctx context.Context, name string, args map[string]any) (string, error) {
+	params := &mcp.CallToolParams{
+		Name:      name,
+		Arguments: args,
+	}
+
+	result, err := c.session.CallTool(ctx, params)
+	if err != nil {
+		return "", fmt.Errorf("call MCP tool %q: %w", name, err)
+	}
+
+	if result.IsError {
+		return fmt.Sprintf("MCP tool %q returned an error: %s", name, contentToText(result.Content)), nil
+	}
+
+	return contentToText(result.Content), nil
+}
+
+func (c *Client) Close() error {
+	return c.session.Close()
+}
+
+func contentToText(contents []mcp.Content) string {
+	var parts []string
+	for _, item := range contents {
+		switch v := item.(type) {
+		case *mcp.TextContent:
+			parts = append(parts, v.Text)
+		default:
+			parts = append(parts, fmt.Sprintf("[unsupported content type: %T]", item))
+		}
+	}
+	if len(parts) == 0 {
+		return ""
+	}
+	return strings.Join(parts, "\n")
+}
diff --git a/internal/mcp/client_test.go b/internal/mcp/client_test.go
new file mode 100644
index 0000000..07aee15
--- /dev/null
+++ b/internal/mcp/client_test.go
@@ -0,0 +1,230 @@
+package mcp
+
+import (
+	"context"
+	"encoding/json"
+	"testing"
+
+	"github.com/modelcontextprotocol/go-sdk/mcp"
+)
+
+func TestContentToText_SingleText(t *testing.T) {
+	contents := []mcp.Content{
+		&mcp.TextContent{Text: "hello"},
+	}
+	got := contentToText(contents)
+	if got != "hello" {
+		t.Errorf("contentToText() = %q, want %q", got, "hello")
+	}
+}
+
+func TestContentToText_MultipleText(t *testing.T) {
+	contents := []mcp.Content{
+		&mcp.TextContent{Text: "line1"},
+		&mcp.TextContent{Text: "line2"},
+	}
+	got := contentToText(contents)
+	want := "line1\nline2"
+	if got != want {
+		t.Errorf("contentToText() = %q, want %q", got, want)
+	}
+}
+
+func TestContentToText_Empty(t *testing.T) {
+	got := contentToText(nil)
+	if got != "" {
+		t.Errorf("contentToText(nil) = %q, want empty", got)
+	}
+
+	got = contentToText([]mcp.Content{})
+	if got != "" {
+		t.Errorf("contentToText([]) = %q, want empty", got)
+	}
+}
+
+func TestContentToText_UnsupportedType(t *testing.T) {
+	contents := []mcp.Content{
+		&mcp.ImageContent{MIMEType: "image/png", Data: []byte("data")},
+	}
+	got := contentToText(contents)
+	if got == "" {
+		t.Error("expected non-empty for unsupported type")
+	}
+}
+
+func TestClient_NameAndTools(t *testing.T) {
+	tools := []*mcp.Tool{{Name: "t1"}, {Name: "t2"}}
+	c := &Client{name: "test-srv", tools: tools}
+
+	if c.Name() != "test-srv" {
+		t.Errorf("Name() = %q, want %q", c.Name(), "test-srv")
+	}
+	if len(c.Tools()) != 2 {
+		t.Errorf("Tools() len = %d, want 2", len(c.Tools()))
+	}
+}
+
+func TestProvider_Execute_Integration(t *testing.T) {
+	server := mcp.NewServer(
+		&mcp.Implementation{Name: "test-server", Version: "v0.0.1"},
+		nil,
+	)
+	server.AddTool(
+		&mcp.Tool{
+			Name:        "greet",
+			Description: "Greets",
+			InputSchema: map[string]any{
+				"type": "object",
+				"properties": map[string]any{
+					"name": map[string]any{"type": "string"},
+				},
+			},
+		},
+		func(_ context.Context, req *mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+			var args struct {
+				Name string `json:"name"`
+			}
+			if err := json.Unmarshal(req.Params.Arguments, &args); err != nil {
+				return nil, err
+			}
+			return &mcp.CallToolResult{
+				Content: []mcp.Content{&mcp.TextContent{Text: "hello " + args.Name}},
+			}, nil
+		},
+	)
+
+	ctx := context.Background()
+	st, ct := mcp.NewInMemoryTransports()
+	if _, err := server.Connect(ctx, st, nil); err != nil {
+		t.Fatalf("server connect: %v", err)
+	}
+	sdkClient := mcp.NewClient(
+		&mcp.Implementation{Name: "test-client", Version: "v0.0.1"},
+		nil,
+	)
+	session, err := sdkClient.Connect(ctx, ct, nil)
+	if err != nil {
+		t.Fatalf("client connect: %v", err)
+	}
+
+	toolsResult, err := session.ListTools(ctx, nil)
+	if err != nil {
+		t.Fatalf("list tools: %v", err)
+	}
+
+	c := &Client{name: "test-srv", session: session, tools: toolsResult.Tools}
+	defer c.Close()
+
+	p := &Provider{toolName: "greet", client: c}
+	result, err := p.Execute(ctx, map[string]any{"name": "world"})
+	if err != nil {
+		t.Fatalf("Execute: %v", err)
+	}
+	if result != "hello world" {
+		t.Errorf("Execute result = %q, want %q", result, "hello world")
+	}
+}
+
+func TestNewClient_Integration(t *testing.T) {
+	server := mcp.NewServer(
+		&mcp.Implementation{Name: "test-server", Version: "v0.0.1"},
+		nil,
+	)
+	server.AddTool(
+		&mcp.Tool{
+			Name:        "echo",
+			Description: "Echoes input",
+			InputSchema: map[string]any{
+				"type": "object",
+				"properties": map[string]any{
+					"message": map[string]any{"type": "string"},
+				},
+			},
+		},
+		func(_ context.Context, req *mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+			var args struct {
+				Message string `json:"message"`
+			}
+			if err := json.Unmarshal(req.Params.Arguments, &args); err != nil {
+				return nil, err
+			}
+			return &mcp.CallToolResult{
+				Content: []mcp.Content{&mcp.TextContent{Text: "echo: " + args.Message}},
+			}, nil
+		},
+	)
+
+	server.AddTool(
+		&mcp.Tool{
+			Name:        "fail",
+			Description: "Always fails",
+			InputSchema: map[string]any{"type": "object"},
+		},
+		func(_ context.Context, _ *mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+			return &mcp.CallToolResult{
+				IsError: true,
+				Content: []mcp.Content{&mcp.TextContent{Text: "something went wrong"}},
+			}, nil
+		},
+	)
+
+	ctx := context.Background()
+	st, ct := mcp.NewInMemoryTransports()
+	if _, err := server.Connect(ctx, st, nil); err != nil {
+		t.Fatalf("server connect: %v", err)
+	}
+
+	sdkClient := mcp.NewClient(
+		&mcp.Implementation{Name: "test-client", Version: "v0.0.1"},
+		nil,
+	)
+	session, err := sdkClient.Connect(ctx, ct, nil)
+	if err != nil {
+		t.Fatalf("client connect: %v", err)
+	}
+
+	toolsResult, err := session.ListTools(ctx, nil)
+	if err != nil {
+		t.Fatalf("list tools: %v", err)
+	}
+
+	c := &Client{
+		name:    "test-srv",
+		session: session,
+		tools:   toolsResult.Tools,
+	}
+	defer c.Close()
+
+	if c.Name() != "test-srv" {
+		t.Errorf("Name() = %q", c.Name())
+	}
+	if len(c.Tools()) != 2 {
+		t.Errorf("Tools() len = %d, want 2", len(c.Tools()))
+	}
+
+	t.Run("CallTool_success", func(t *testing.T) {
+		result, err := c.CallTool(ctx, "echo", map[string]any{"message": "hi"})
+		if err != nil {
+			t.Fatalf("CallTool: %v", err)
+		}
+		if result != "echo: hi" {
+			t.Errorf("CallTool result = %q, want %q", result, "echo: hi")
+		}
+	})
+
+	t.Run("CallTool_error_result", func(t *testing.T) {
+		result, err := c.CallTool(ctx, "fail", nil)
+		if err != nil {
+			t.Fatalf("CallTool: %v", err)
+		}
+		if result == "" {
+			t.Error("expected non-empty error message")
+		}
+	})
+
+	t.Run("Close", func(t *testing.T) {
+		if err := c.Close(); err != nil {
+			t.Errorf("Close: %v", err)
+		}
+	})
+}
diff --git a/internal/mcp/provider.go b/internal/mcp/provider.go
new file mode 100644
index 0000000..8fe0f0d
--- /dev/null
+++ b/internal/mcp/provider.go
@@ -0,0 +1,115 @@
+package mcp
+
+import (
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/modelcontextprotocol/go-sdk/mcp"
+	"github.com/open-code-review/open-code-review/internal/llm"
+	"github.com/open-code-review/open-code-review/internal/tool"
+)
+
+// Provider adapts a single MCP tool to the tool.Provider interface.
+type Provider struct {
+	toolName string
+	client   *Client
+}
+
+func (p *Provider) Tool() tool.Tool {
+	return tool.Dynamic(p.toolName)
+}
+
+func (p *Provider) Execute(ctx context.Context, args map[string]any) (string, error) {
+	return p.client.CallTool(ctx, p.toolName, args)
+}
+
+// RegisterAll registers tools from the MCP client into the tool registry.
+// When allowedTools is non-empty, only tools whose names appear in the list are registered.
+// Tools whose names conflict with built-in or already-registered tools are skipped with a warning.
+func RegisterAll(reg *tool.Registry, c *Client, allowedTools []string) {
+	allowed := make(map[string]struct{}, len(allowedTools))
+	for _, name := range allowedTools {
+		allowed[name] = struct{}{}
+	}
+	filtering := len(allowed) > 0
+
+	matched := make(map[string]struct{})
+	for _, t := range c.Tools() {
+		if filtering {
+			if _, ok := allowed[t.Name]; !ok {
+				continue
+			}
+			matched[t.Name] = struct{}{}
+		}
+		if tool.IsReserved(t.Name) {
+			fmt.Fprintf(os.Stderr, "[ocr] WARNING: MCP server %q tool %q conflicts with built-in tool, skipping\n", c.Name(), t.Name)
+			continue
+		}
+		if _, exists := reg.Get(t.Name); exists {
+			fmt.Fprintf(os.Stderr, "[ocr] WARNING: MCP server %q tool %q conflicts with already-registered tool, skipping\n", c.Name(), t.Name)
+			continue
+		}
+		reg.Register(&Provider{
+			toolName: t.Name,
+			client:   c,
+		})
+	}
+
+	for name := range allowed {
+		if _, ok := matched[name]; !ok {
+			fmt.Fprintf(os.Stderr, "[ocr] WARNING: MCP server %q allowed tool %q not found in server's tool list\n", c.Name(), name)
+		}
+	}
+}
+
+// ToToolDef converts an MCP tool definition to an llm.ToolDef.
+func ToToolDef(t *mcp.Tool) llm.ToolDef {
+	params := map[string]any{"type": "object"}
+
+	switch schema := t.InputSchema.(type) {
+	case map[string]any:
+		for k, v := range schema {
+			params[k] = v
+		}
+		if _, ok := params["type"]; !ok {
+			params["type"] = "object"
+		}
+	case nil:
+		// No schema — keep the default {"type": "object"}.
+	default:
+		fmt.Fprintf(os.Stderr, "[ocr] WARNING: MCP tool %q has unexpected InputSchema type %T, using empty object schema\n", t.Name, t.InputSchema)
+	}
+
+	return llm.ToolDef{
+		Type: "function",
+		Function: llm.FunctionDef{
+			Name:        t.Name,
+			Description: t.Description,
+			Parameters:  params,
+		},
+	}
+}
+
+// CollectToolDefs gathers tool definitions from MCP clients, filtering out
+// tools that conflict with built-in tools or were not successfully registered.
+func CollectToolDefs(clients []*Client, reg *tool.Registry) []llm.ToolDef {
+	var defs []llm.ToolDef
+	seen := make(map[string]struct{})
+	for _, c := range clients {
+		for _, t := range c.Tools() {
+			if tool.IsReserved(t.Name) {
+				continue
+			}
+			if _, exists := reg.Get(t.Name); !exists {
+				continue
+			}
+			if _, dup := seen[t.Name]; dup {
+				continue
+			}
+			seen[t.Name] = struct{}{}
+			defs = append(defs, ToToolDef(t))
+		}
+	}
+	return defs
+}
diff --git a/internal/mcp/provider_test.go b/internal/mcp/provider_test.go
new file mode 100644
index 0000000..1a5cc48
--- /dev/null
+++ b/internal/mcp/provider_test.go
@@ -0,0 +1,242 @@
+package mcp
+
+import (
+	"testing"
+
+	"github.com/modelcontextprotocol/go-sdk/mcp"
+	"github.com/open-code-review/open-code-review/internal/llm"
+	"github.com/open-code-review/open-code-review/internal/tool"
+)
+
+func newTestClient(name string, tools []*mcp.Tool) *Client {
+	return &Client{name: name, tools: tools}
+}
+
+func TestProvider_Tool(t *testing.T) {
+	c := newTestClient("srv", nil)
+	p := &Provider{toolName: "my_tool", client: c}
+	got := p.Tool()
+	if got.Name() != "my_tool" {
+		t.Errorf("Tool().Name() = %q, want %q", got.Name(), "my_tool")
+	}
+}
+
+func TestRegisterAll_Basic(t *testing.T) {
+	tools := []*mcp.Tool{
+		{Name: "alpha"},
+		{Name: "beta"},
+	}
+	c := newTestClient("srv", tools)
+	reg := tool.NewRegistry()
+
+	RegisterAll(reg, c, nil)
+
+	for _, name := range []string{"alpha", "beta"} {
+		if _, ok := reg.Get(name); !ok {
+			t.Errorf("expected tool %q to be registered", name)
+		}
+	}
+}
+
+func TestRegisterAll_AllowedFilter(t *testing.T) {
+	tools := []*mcp.Tool{
+		{Name: "alpha"},
+		{Name: "beta"},
+		{Name: "gamma"},
+	}
+	c := newTestClient("srv", tools)
+	reg := tool.NewRegistry()
+
+	RegisterAll(reg, c, []string{"alpha", "gamma"})
+
+	if _, ok := reg.Get("alpha"); !ok {
+		t.Error("expected alpha to be registered")
+	}
+	if _, ok := reg.Get("beta"); ok {
+		t.Error("expected beta to be filtered out")
+	}
+	if _, ok := reg.Get("gamma"); !ok {
+		t.Error("expected gamma to be registered")
+	}
+}
+
+func TestRegisterAll_SkipsReservedTools(t *testing.T) {
+	tools := []*mcp.Tool{
+		{Name: "file_read"},
+		{Name: "custom_tool"},
+	}
+	c := newTestClient("srv", tools)
+	reg := tool.NewRegistry()
+
+	RegisterAll(reg, c, nil)
+
+	if _, ok := reg.Get("file_read"); ok {
+		t.Error("reserved tool file_read should not be registered")
+	}
+	if _, ok := reg.Get("custom_tool"); !ok {
+		t.Error("expected custom_tool to be registered")
+	}
+}
+
+func TestRegisterAll_SkipsDuplicateTools(t *testing.T) {
+	tools := []*mcp.Tool{{Name: "dup_tool"}}
+	c := newTestClient("srv", tools)
+	reg := tool.NewRegistry()
+
+	stub := tool.NewStub(tool.Dynamic("dup_tool"))
+	reg.Register(stub)
+
+	RegisterAll(reg, c, nil)
+
+	got, ok := reg.Get("dup_tool")
+	if !ok {
+		t.Fatal("expected dup_tool to be registered")
+	}
+	if _, isProvider := got.(*Provider); isProvider {
+		t.Error("expected dup_tool to remain the original stub, not MCP provider")
+	}
+}
+
+func TestRegisterAll_WarnsUnmatchedAllowed(t *testing.T) {
+	tools := []*mcp.Tool{{Name: "alpha"}}
+	c := newTestClient("srv", tools)
+	reg := tool.NewRegistry()
+
+	RegisterAll(reg, c, []string{"alpha", "nonexistent"})
+
+	if _, ok := reg.Get("alpha"); !ok {
+		t.Error("expected alpha to be registered")
+	}
+}
+
+func TestToToolDef_MapSchema(t *testing.T) {
+	mt := &mcp.Tool{
+		Name:        "search",
+		Description: "Search things",
+		InputSchema: map[string]any{
+			"type": "object",
+			"properties": map[string]any{
+				"query": map[string]any{"type": "string"},
+			},
+		},
+	}
+
+	got := ToToolDef(mt)
+
+	want := llm.ToolDef{
+		Type: "function",
+		Function: llm.FunctionDef{
+			Name:        "search",
+			Description: "Search things",
+		},
+	}
+	if got.Type != want.Type || got.Function.Name != want.Function.Name || got.Function.Description != want.Function.Description {
+		t.Errorf("ToToolDef() basic fields mismatch: got %+v", got)
+	}
+	if got.Function.Parameters["type"] != "object" {
+		t.Errorf("expected type=object, got %v", got.Function.Parameters["type"])
+	}
+	if got.Function.Parameters["properties"] == nil {
+		t.Error("expected properties to be set")
+	}
+}
+
+func TestToToolDef_NilSchema(t *testing.T) {
+	mt := &mcp.Tool{
+		Name:        "noop",
+		InputSchema: nil,
+	}
+
+	got := ToToolDef(mt)
+
+	if got.Function.Parameters["type"] != "object" {
+		t.Errorf("expected default type=object, got %v", got.Function.Parameters["type"])
+	}
+}
+
+func TestToToolDef_UnexpectedSchemaType(t *testing.T) {
+	mt := &mcp.Tool{
+		Name:        "weird",
+		InputSchema: "not-a-map",
+	}
+
+	got := ToToolDef(mt)
+
+	if got.Function.Parameters["type"] != "object" {
+		t.Errorf("expected fallback type=object, got %v", got.Function.Parameters["type"])
+	}
+}
+
+func TestCollectToolDefs_Basic(t *testing.T) {
+	tools := []*mcp.Tool{
+		{Name: "alpha", Description: "A"},
+		{Name: "beta", Description: "B"},
+	}
+	c := newTestClient("srv", tools)
+	reg := tool.NewRegistry()
+	RegisterAll(reg, c, nil)
+
+	defs := CollectToolDefs([]*Client{c}, reg)
+
+	if len(defs) != 2 {
+		t.Fatalf("expected 2 defs, got %d", len(defs))
+	}
+	names := map[string]bool{}
+	for _, d := range defs {
+		names[d.Function.Name] = true
+	}
+	if !names["alpha"] || !names["beta"] {
+		t.Errorf("expected alpha and beta in defs, got %v", names)
+	}
+}
+
+func TestCollectToolDefs_FiltersReserved(t *testing.T) {
+	tools := []*mcp.Tool{
+		{Name: "file_read"},
+		{Name: "custom"},
+	}
+	c := newTestClient("srv", tools)
+	reg := tool.NewRegistry()
+	RegisterAll(reg, c, nil)
+
+	defs := CollectToolDefs([]*Client{c}, reg)
+
+	for _, d := range defs {
+		if d.Function.Name == "file_read" {
+			t.Error("reserved tool file_read should not appear in defs")
+		}
+	}
+}
+
+func TestCollectToolDefs_FiltersUnregistered(t *testing.T) {
+	tools := []*mcp.Tool{
+		{Name: "registered_tool"},
+		{Name: "unregistered_tool"},
+	}
+	c := newTestClient("srv", tools)
+	reg := tool.NewRegistry()
+	reg.Register(&Provider{toolName: "registered_tool", client: c})
+
+	defs := CollectToolDefs([]*Client{c}, reg)
+
+	if len(defs) != 1 {
+		t.Fatalf("expected 1 def, got %d", len(defs))
+	}
+	if defs[0].Function.Name != "registered_tool" {
+		t.Errorf("expected registered_tool, got %s", defs[0].Function.Name)
+	}
+}
+
+func TestCollectToolDefs_Dedup(t *testing.T) {
+	tools := []*mcp.Tool{{Name: "shared", Description: "A"}}
+	c1 := newTestClient("srv1", tools)
+	c2 := newTestClient("srv2", tools)
+	reg := tool.NewRegistry()
+	reg.Register(&Provider{toolName: "shared", client: c1})
+
+	defs := CollectToolDefs([]*Client{c1, c2}, reg)
+
+	if len(defs) != 1 {
+		t.Errorf("expected 1 deduped def, got %d", len(defs))
+	}
+}
diff --git a/internal/mcp/stdio_test.go b/internal/mcp/stdio_test.go
new file mode 100644
index 0000000..ea9f3d0
--- /dev/null
+++ b/internal/mcp/stdio_test.go
@@ -0,0 +1,118 @@
+package mcp
+
+import (
+	"context"
+	"encoding/json"
+	"log"
+	"os"
+	"runtime"
+	"testing"
+
+	"github.com/modelcontextprotocol/go-sdk/mcp"
+)
+
+const runAsServerEnv = "_OCR_MCP_TEST_SERVER"
+
+func TestMain(m *testing.M) {
+	if os.Getenv(runAsServerEnv) != "" {
+		runTestMCPServer()
+		return
+	}
+	os.Exit(m.Run())
+}
+
+func runTestMCPServer() {
+	server := mcp.NewServer(
+		&mcp.Implementation{Name: "test-server", Version: "v0.0.1"},
+		nil,
+	)
+	server.AddTool(
+		&mcp.Tool{
+			Name:        "echo",
+			Description: "Echoes input",
+			InputSchema: map[string]any{
+				"type": "object",
+				"properties": map[string]any{
+					"message": map[string]any{"type": "string"},
+				},
+			},
+		},
+		func(_ context.Context, req *mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+			var args struct {
+				Message string `json:"message"`
+			}
+			if err := json.Unmarshal(req.Params.Arguments, &args); err != nil {
+				return nil, err
+			}
+			return &mcp.CallToolResult{
+				Content: []mcp.Content{&mcp.TextContent{Text: "echo: " + args.Message}},
+			}, nil
+		},
+	)
+
+	if err := server.Run(context.Background(), &mcp.StdioTransport{}); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func TestNewClient_Stdio(t *testing.T) {
+	requireExec(t)
+
+	exe, err := os.Executable()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ctx := context.Background()
+	c, err := NewClient(ctx, "test-srv", exe, nil, []string{runAsServerEnv + "=1"}, "", "v0.0.1")
+	if err != nil {
+		t.Fatalf("NewClient: %v", err)
+	}
+	defer c.Close()
+
+	if c.Name() != "test-srv" {
+		t.Errorf("Name() = %q, want %q", c.Name(), "test-srv")
+	}
+
+	found := false
+	for _, tool := range c.Tools() {
+		if tool.Name == "echo" {
+			found = true
+			break
+		}
+	}
+	if !found {
+		t.Error("expected echo tool in Tools()")
+	}
+
+	result, err := c.CallTool(ctx, "echo", map[string]any{"message": "hello"})
+	if err != nil {
+		t.Fatalf("CallTool: %v", err)
+	}
+	if result != "echo: hello" {
+		t.Errorf("CallTool result = %q, want %q", result, "echo: hello")
+	}
+
+	if err := c.Close(); err != nil {
+		t.Errorf("Close: %v", err)
+	}
+}
+
+func TestNewClient_Stdio_BadCommand(t *testing.T) {
+	requireExec(t)
+
+	ctx := context.Background()
+	_, err := NewClient(ctx, "bad", "/nonexistent/mcp-server-binary", nil, nil, "", "v0.0.1")
+	if err == nil {
+		t.Fatal("expected error for bad command, got nil")
+	}
+}
+
+func requireExec(t *testing.T) {
+	t.Helper()
+	switch runtime.GOOS {
+	case "darwin", "linux", "windows":
+	default:
+		t.Skip("unsupported OS for subprocess test")
+	}
+}
diff --git a/internal/tool/definitions.go b/internal/tool/definitions.go
index cf24f99..6cbab77 100644
--- a/internal/tool/definitions.go
+++ b/internal/tool/definitions.go
@@ -3,6 +3,7 @@ package tool
 import (
 	"context"
 	"errors"
+	"fmt"
 )
 
 // Tool represents a single review tool.
@@ -33,6 +34,27 @@ func allTools() []Tool {
 	return []Tool{Unknown, TaskDone, CodeComment, FileRead, FileFind, FileReadDiff, CodeSearch}
 }
 
+// IsReserved reports whether name matches any built-in tool name (including Unknown).
+func IsReserved(name string) bool {
+	for _, t := range allTools() {
+		if t.name == name {
+			return true
+		}
+	}
+	return false
+}
+
+// Dynamic creates a Tool with the given name for dynamically discovered tools (e.g. MCP).
+func Dynamic(name string) Tool {
+	if name == "" {
+		panic("tool: Dynamic called with empty name")
+	}
+	if IsReserved(name) {
+		panic(fmt.Sprintf("tool: Dynamic called with reserved tool name %q", name))
+	}
+	return Tool{name: name}
+}
+
 // Name returns the tool's identifier name.
 func (t Tool) Name() string { return t.name }
 
diff --git a/internal/tool/definitions_test.go b/internal/tool/definitions_test.go
index a1f1af3..ae3cf96 100644
--- a/internal/tool/definitions_test.go
+++ b/internal/tool/definitions_test.go
@@ -86,6 +86,47 @@ func TestRegistry_GetAfterFreeze(t *testing.T) {
 	}
 }
 
+func TestIsReserved(t *testing.T) {
+	reserved := []string{"unknown", "task_done", "code_comment", "file_read", "file_find", "file_read_diff", "code_search"}
+	for _, name := range reserved {
+		if !IsReserved(name) {
+			t.Errorf("IsReserved(%q) = false, want true", name)
+		}
+	}
+
+	nonReserved := []string{"custom_tool", "my_tool", "search", ""}
+	for _, name := range nonReserved {
+		if IsReserved(name) {
+			t.Errorf("IsReserved(%q) = true, want false", name)
+		}
+	}
+}
+
+func TestDynamic(t *testing.T) {
+	tool := Dynamic("my_custom_tool")
+	if tool.Name() != "my_custom_tool" {
+		t.Errorf("Dynamic().Name() = %q, want %q", tool.Name(), "my_custom_tool")
+	}
+}
+
+func TestDynamic_PanicsOnEmpty(t *testing.T) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Error("expected panic for empty name")
+		}
+	}()
+	Dynamic("")
+}
+
+func TestDynamic_PanicsOnReserved(t *testing.T) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Error("expected panic for reserved name")
+		}
+	}()
+	Dynamic("file_read")
+}
+
 type dummyProvider struct{}
 
 func (d *dummyProvider) Tool() Tool { return CodeSearch }