fix: recover malformed tool calls from GLM/Minimax models instead of rejecting them (#10230)

Co-authored-by: Douwe M Osinga <douwe@sidewalklabs.com>

crates/goose-provider-types/src/formats/openai.rs

@@ -709,13 +709,13 @@ pub fn response_to_message(response: &Value) -> anyhow::Result<Message> {
                     })
                     .filter(|m: &serde_json::Map<String, Value>| !m.is_empty());
 
-                if !is_valid_function_name(&function_name) {
+                if function_name.is_empty() {
                     let error = ErrorData {
                         code: ErrorCode::INVALID_REQUEST,
-                        message: Cow::from(format!(
-                            "The provided function name '{}' had invalid characters, it must match this regex [a-zA-Z0-9_-]+",
-                            function_name
-                        )),
+                        message: Cow::from(
+                            "The provided function name was empty; a tool call must name a tool"
+                                .to_string(),
+                        ),
                         data: None,
                     };
                     content.push(MessageContent::tool_request_with_metadata(
@@ -723,7 +723,8 @@ pub fn response_to_message(response: &Value) -> anyhow::Result<Message> {
                         Err(error),
                         metadata.as_ref(),
                     ));
-                } else {
+                    continue;
+                }
                 match parse_tool_arguments(&arguments_str) {
                     Some(params) if params.is_object() => {
                         content.push(MessageContent::tool_request_with_metadata(
@@ -733,10 +734,6 @@ pub fn response_to_message(response: &Value) -> anyhow::Result<Message> {
                             metadata.as_ref(),
                         ));
                     }
-                        // Valid JSON but NOT an object (a bare array/string/number).
-                        // Weaker models emit this; surface a tool error so the model
-                        // retries with a proper object instead of crashing the run
-                        // (rmcp's `object()` debug-asserts on non-objects).
                     Some(other) => {
                         let error = ErrorData {
                             code: ErrorCode::INVALID_PARAMS,
@@ -756,8 +753,8 @@ pub fn response_to_message(response: &Value) -> anyhow::Result<Message> {
                         ));
                     }
                     None => {
-                            let message_text = truncation_error_message(&arguments_str)
-                                .unwrap_or_else(|| {
+                        let message_text =
+                            truncation_error_message(&arguments_str).unwrap_or_else(|| {
                                 format!("Could not interpret tool use parameters for id {id}")
                             });
                         let error = ErrorData {
@@ -775,7 +772,6 @@ pub fn response_to_message(response: &Value) -> anyhow::Result<Message> {
             }
         }
     }
-    }
 
     Ok(Message::new(
         Role::Assistant,
@@ -2012,10 +2008,9 @@ mod tests {
     }
 
     #[test]
-    fn test_response_to_message_invalid_func_name() -> anyhow::Result<()> {
+    fn test_response_to_message_empty_func_name() -> anyhow::Result<()> {
         let mut response: Value = serde_json::from_str(OPENAI_TOOL_USE_RESPONSE)?;
-        response["choices"][0]["message"]["tool_calls"][0]["function"]["name"] =
-            json!("invalid fn");
+        response["choices"][0]["message"]["tool_calls"][0]["function"]["name"] = json!("");
 
         let message = response_to_message(&response)?;
 
@@ -2028,7 +2023,7 @@ mod tests {
                 }) => {
                     assert!(msg.starts_with("The provided function name"));
                 }
-                _ => panic!("Expected ToolNotFound error"),
+                _ => panic!("Expected invalid-request error for empty name"),
             }
         } else {
             panic!("Expected ToolRequest content");
@@ -2037,6 +2032,48 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn test_response_to_message_passes_names_through_to_dispatch() -> anyhow::Result<()> {
+        for name in [
+            "developer.shell",
+            "functions.example_fn",
+            "example fn",
+            "???!",
+        ] {
+            let mut response: Value = serde_json::from_str(OPENAI_TOOL_USE_RESPONSE)?;
+            response["choices"][0]["message"]["tool_calls"][0]["function"]["name"] = json!(name);
+
+            let message = response_to_message(&response)?;
+
+            if let MessageContent::ToolRequest(request) = &message.content[0] {
+                let tool_call = request.tool_call.as_ref().expect("tool call should parse");
+                assert_eq!(tool_call.name, name, "name must pass through verbatim");
+            } else {
+                panic!("Expected ToolRequest content");
+            }
+        }
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_response_to_message_fenced_arguments() -> anyhow::Result<()> {
+        let mut response: Value = serde_json::from_str(OPENAI_TOOL_USE_RESPONSE)?;
+        response["choices"][0]["message"]["tool_calls"][0]["function"]["arguments"] =
+            json!("```json\n{\"param\": \"value\"}\n```");
+
+        let message = response_to_message(&response)?;
+
+        if let MessageContent::ToolRequest(request) = &message.content[0] {
+            let tool_call = request.tool_call.as_ref().expect("tool call should parse");
+            assert_eq!(tool_call.arguments, Some(object!({"param": "value"})));
+        } else {
+            panic!("Expected ToolRequest content");
+        }
+
+        Ok(())
+    }
+
     #[test]
     fn test_response_to_message_json_decode_error() -> anyhow::Result<()> {
         let mut response: Value = serde_json::from_str(OPENAI_TOOL_USE_RESPONSE)?;
@@ -3825,6 +3862,68 @@ data: [DONE]"#;
         Ok(())
     }
 
+    #[tokio::test]
+    async fn test_streaming_tool_call_dotted_name_passes_through() -> anyhow::Result<()> {
+        let response_lines = concat!(
+            "data: {\"id\":\"x\",\"object\":\"chat.completion.chunk\",\"model\":\"m\",\"choices\":[{\"index\":0,\"delta\":{\"role\":\"assistant\",\"tool_calls\":[{\"index\":0,\"id\":\"tc1\",\"type\":\"function\",\"function\":{\"name\":\"ext__db.query\",\"arguments\":\"{\\\"command\\\": \\\"ls\\\"}\"}}]},\"finish_reason\":\"tool_calls\"}]}\n",
+            "data: [DONE]"
+        );
+        let lines: Vec<String> = response_lines.lines().map(|s| s.to_string()).collect();
+        let response_stream = tokio_stream::iter(lines.into_iter().map(Ok));
+        let mut messages = std::pin::pin!(response_to_streaming_message(response_stream));
+
+        let mut tool_calls = Vec::new();
+        while let Some(result) = messages.next().await {
+            let (message, _usage) = result?;
+            if let Some(msg) = message {
+                for content in &msg.content {
+                    if let MessageContent::ToolRequest(request) = content {
+                        let tool_call = request.tool_call.as_ref().expect("tool call should parse");
+                        tool_calls.push((tool_call.name.to_string(), tool_call.arguments.clone()));
+                    }
+                }
+            }
+        }
+
+        assert_eq!(tool_calls.len(), 1);
+        assert_eq!(tool_calls[0].0, "ext__db.query");
+        assert_eq!(tool_calls[0].1, Some(object!({"command": "ls"})));
+        Ok(())
+    }
+
+    #[tokio::test]
+    async fn test_streaming_tool_call_degenerate_name_passes_through() -> anyhow::Result<()> {
+        let response_lines = concat!(
+            "data: {\"id\":\"x\",\"object\":\"chat.completion.chunk\",\"model\":\"m\",\"choices\":[{\"index\":0,\"delta\":{\"role\":\"assistant\",\"tool_calls\":[{\"index\":0,\"id\":\"tc1\",\"type\":\"function\",\"function\":{\"name\":\"???\",\"arguments\":\"{}\"}}]},\"finish_reason\":\"tool_calls\"}]}\n",
+            "data: [DONE]"
+        );
+        let lines: Vec<String> = response_lines.lines().map(|s| s.to_string()).collect();
+        let response_stream = tokio_stream::iter(lines.into_iter().map(Ok));
+        let mut messages = std::pin::pin!(response_to_streaming_message(response_stream));
+
+        let mut names = Vec::new();
+        while let Some(result) = messages.next().await {
+            let (message, _usage) = result?;
+            if let Some(msg) = message {
+                for content in &msg.content {
+                    if let MessageContent::ToolRequest(request) = content {
+                        names.push(
+                            request
+                                .tool_call
+                                .as_ref()
+                                .expect("passes through")
+                                .name
+                                .to_string(),
+                        );
+                    }
+                }
+            }
+        }
+
+        assert_eq!(names, vec!["???".to_string()]);
+        Ok(())
+    }
+
     #[tokio::test]
     async fn test_streaming_multiple_tool_calls_without_tool_call_index() -> anyhow::Result<()> {
         let response_lines = concat!(

crates/goose-provider-types/src/json.rs

@@ -215,6 +215,56 @@ pub fn truncation_error_message(args: &str) -> Option<String> {
     ))
 }
 
+fn strip_json_wrapper(args: &str) -> Option<&str> {
+    let trimmed = args.trim();
+
+    if let Some(rest) = trimmed.strip_prefix("```") {
+        let body = rest.strip_suffix("```")?.trim_start();
+        let body = body
+            .strip_prefix("json")
+            .or_else(|| body.strip_prefix("JSON"))
+            .unwrap_or(body);
+        return Some(body.trim());
+    }
+
+    if trimmed.starts_with('<') && !trimmed.starts_with("</") {
+        let open_end = trimmed.find('>')?;
+        let tag_name = trimmed.get(1..open_end)?.split_whitespace().next()?;
+        if tag_name.is_empty()
+            || !tag_name
+                .chars()
+                .all(|c| c.is_ascii_alphanumeric() || c == '_' || c == '-')
+        {
+            return None;
+        }
+        let closing = format!("</{tag_name}>");
+        let body = trimmed
+            .get(open_end + 1..)?
+            .trim_end()
+            .strip_suffix(&closing)?;
+        return Some(body.trim());
+    }
+
+    None
+}
+
+fn unwrap_double_encoded_object(value: serde_json::Value) -> serde_json::Value {
+    let serde_json::Value::String(s) = &value else {
+        return value;
+    };
+
+    let mut current = s.trim().to_string();
+    for _ in 0..3 {
+        match serde_json::from_str::<serde_json::Value>(&current) {
+            Ok(inner @ serde_json::Value::Object(_)) => return inner,
+            Ok(serde_json::Value::String(inner)) => current = inner.trim().to_string(),
+            _ => break,
+        }
+    }
+
+    value
+}
+
 /// Parse tool-call arguments, returning `None` when the input looks truncated
 /// so callers can surface an actionable error rather than invoking a tool with
 /// incomplete arguments. Non-truncated malformation (e.g. unescaped control
@@ -225,12 +275,23 @@ pub fn parse_tool_arguments(args: &str) -> Option<serde_json::Value> {
     }
 
     if let Ok(value) = serde_json::from_str::<serde_json::Value>(args) {
-        return Some(value);
+        return Some(unwrap_double_encoded_object(value));
+    }
+
+    if let Some(inner) = strip_json_wrapper(args) {
+        if let Ok(value) = serde_json::from_str::<serde_json::Value>(inner) {
+            return Some(unwrap_double_encoded_object(value));
+        }
+        if !looks_truncated(inner) {
+            if let Ok(value) = safely_parse_json(inner) {
+                return Some(unwrap_double_encoded_object(value));
+            }
+        }
     }
 
     if !looks_truncated(args) {
         if let Ok(value) = safely_parse_json(args) {
-            return Some(value);
+            return Some(unwrap_double_encoded_object(value));
         }
     }
 
@@ -416,6 +477,78 @@ mod tests {
         assert!(msg.contains("cut off at:"), "msg: {msg}");
     }
 
+    #[test]
+    fn test_parse_tool_arguments_markdown_fenced() {
+        let fenced = "```json\n{\"command\": \"ls\"}\n```";
+        let parsed = parse_tool_arguments(fenced).expect("fenced JSON should parse");
+        assert_eq!(parsed["command"], "ls");
+
+        let fenced_no_lang = "```\n{\"command\": \"ls\"}\n```";
+        let parsed = parse_tool_arguments(fenced_no_lang).expect("fenced JSON should parse");
+        assert_eq!(parsed["command"], "ls");
+
+        let fenced_inline = "```json{\"command\": \"ls\"}```";
+        let parsed = parse_tool_arguments(fenced_inline).expect("fenced JSON should parse");
+        assert_eq!(parsed["command"], "ls");
+    }
+
+    #[test]
+    fn test_parse_tool_arguments_double_encoded() {
+        let double_encoded = r#""{\"command\": \"ls\"}""#;
+        let parsed = parse_tool_arguments(double_encoded).expect("double-encoded should parse");
+        assert!(parsed.is_object(), "expected object, got {parsed:?}");
+        assert_eq!(parsed["command"], "ls");
+
+        let twice = serde_json::to_string(&serde_json::json!(r#"{"command": "ls"}"#)).unwrap();
+        let twice = serde_json::to_string(&serde_json::json!(twice)).unwrap();
+        let parsed = parse_tool_arguments(&twice).expect("twice-encoded should parse");
+        assert!(parsed.is_object(), "expected object, got {parsed:?}");
+        assert_eq!(parsed["command"], "ls");
+    }
+
+    #[test]
+    fn test_parse_tool_arguments_xml_wrapped() {
+        let wrapped = r#"<tool_call>{"command": "ls"}</tool_call>"#;
+        let parsed = parse_tool_arguments(wrapped).expect("xml-wrapped JSON should parse");
+        assert_eq!(parsed["command"], "ls");
+
+        let with_attrs = r#"<tool_call id="1">{"command": "ls"}</tool_call>"#;
+        let parsed = parse_tool_arguments(with_attrs).expect("xml-wrapped JSON should parse");
+        assert_eq!(parsed["command"], "ls");
+    }
+
+    #[test]
+    fn test_parse_tool_arguments_unrecoverable_wrappers_still_fail() {
+        assert!(parse_tool_arguments(r#"<a><b>{"x": 1}</b></a>"#).is_none());
+        assert!(parse_tool_arguments("```json\n{\"x\": 1}\n``` extra").is_none());
+        assert!(parse_tool_arguments(r#"<tool_call>{"x": 1}</other>"#).is_none());
+        assert!(parse_tool_arguments(r#"</tool_call>"#).is_none());
+        assert!(parse_tool_arguments("```").is_none());
+    }
+
+    #[test]
+    fn test_parse_tool_arguments_non_object_json_unchanged() {
+        assert_eq!(parse_tool_arguments("null"), Some(serde_json::Value::Null));
+        assert_eq!(parse_tool_arguments("42"), Some(serde_json::json!(42)));
+        assert_eq!(
+            parse_tool_arguments("[1, 2]"),
+            Some(serde_json::json!([1, 2]))
+        );
+    }
+
+    #[test]
+    fn test_parse_tool_arguments_plain_string_preserved() {
+        let plain = r#""hello""#;
+        let parsed = parse_tool_arguments(plain).expect("valid JSON string should parse");
+        assert_eq!(parsed, serde_json::json!("hello"));
+    }
+
+    #[test]
+    fn test_parse_tool_arguments_fenced_truncated_still_fails() {
+        let truncated = "```json\n{\"path\": \"/report.md\", \"content\": \"# cut";
+        assert!(parse_tool_arguments(truncated).is_none());
+    }
+
     #[test]
     fn test_truncation_error_message_malformed() {
         // Malformed JSON that ends with } (not truncated, just broken).

crates/goose/src/agents/extension_manager.rs

@@ -275,6 +275,36 @@ pub fn get_tool_owner(tool: &Tool) -> Option<String> {
         .map(|s| s.to_string())
 }
 
+fn recover_mangled_tool_name<'a>(
+    emitted: &str,
+    tool_names: impl Iterator<Item = &'a str>,
+) -> Option<String> {
+    let trimmed = emitted.trim();
+    let stripped = trimmed
+        .strip_prefix("functions.")
+        .or_else(|| trimmed.strip_prefix("functions:"))
+        .unwrap_or(trimmed);
+
+    let mut matched: Option<&str> = None;
+    for name in tool_names {
+        let separator_mangled = name
+            .split_once("__")
+            .map(|(extension, tool)| format!("{extension}.{tool}"));
+
+        let matches = stripped == name || separator_mangled.as_deref() == Some(stripped);
+        if name == emitted || !matches {
+            continue;
+        }
+
+        match matched {
+            None => matched = Some(name),
+            Some(prev) if prev == name => {}
+            Some(_) => return None,
+        }
+    }
+    matched.map(|s| s.to_string())
+}
+
 fn get_tool_meta_value(tool: &Tool) -> Option<Value> {
     tool.meta.as_ref().map(|meta| Value::Object(meta.0.clone()))
 }
@@ -1673,30 +1703,29 @@ impl ExtensionManager {
             )
         })?;
 
-        if let Some(tool) = tools.iter().find(|t| *t.name == *tool_name) {
+        let mut name = tool_name.to_string();
+        let mut recovery_attempted = false;
+        loop {
+            if let Some(tool) = tools.iter().find(|t| *t.name == *name) {
                 let owner = get_tool_owner(tool)
-                .or_else(|| {
-                    tool_name
-                        .split_once("__")
-                        .map(|(prefix, _)| name_to_key(prefix))
-                })
+                    .or_else(|| name.split_once("__").map(|(prefix, _)| name_to_key(prefix)))
                     .ok_or_else(|| {
                         ErrorData::new(
                             ErrorCode::RESOURCE_NOT_FOUND,
-                        format!("Tool '{}' has no owner", tool_name),
+                            format!("Tool '{}' has no owner", name),
                             None,
                         )
                     })?;
 
-            let actual_tool_name = tool_name
+                let actual_tool_name = name
                     .strip_prefix(&format!("{owner}__"))
-                .unwrap_or(tool_name)
+                    .unwrap_or(&name)
                     .to_string();
 
                 let client = self.get_server_client(&owner).await.ok_or_else(|| {
                     ErrorData::new(
                         ErrorCode::RESOURCE_NOT_FOUND,
-                    format!("Extension '{}' not found for tool '{}'", owner, tool_name),
+                        format!("Extension '{}' not found for tool '{}'", owner, name),
                         None,
                     )
                 })?;
@@ -1711,11 +1740,11 @@ impl ExtensionManager {
                 });
             }
 
-        if let Some((prefix, actual)) = tool_name.split_once("__") {
+            if let Some((prefix, actual)) = name.split_once("__") {
                 let owner = name_to_key(prefix);
                 if let Some(client) = self.get_server_client(&owner).await {
                     return Ok(ResolvedTool {
-                    tool_name: tool_name.to_string(),
+                        tool_name: name.to_string(),
                         extension_name: owner,
                         actual_tool_name: actual.to_string(),
                         client,
@@ -1725,6 +1754,19 @@ impl ExtensionManager {
                 }
             }
 
+            if !recovery_attempted {
+                recovery_attempted = true;
+                if let Some(recovered) =
+                    recover_mangled_tool_name(&name, tools.iter().map(|t| t.name.as_ref()))
+                {
+                    name = recovered;
+                    continue;
+                }
+            }
+
+            break;
+        }
+
         let available = tools
             .iter()
             .map(|t| t.name.as_ref())
@@ -2594,6 +2636,198 @@ mod tests {
         );
     }
 
+    struct MockDottedClient {}
+
+    #[async_trait::async_trait]
+    impl McpClientTrait for MockDottedClient {
+        fn get_info(&self) -> Option<&InitializeResult> {
+            None
+        }
+
+        async fn list_resources(
+            &self,
+            _session_id: &str,
+            _next_cursor: Option<String>,
+            _cancellation_token: CancellationToken,
+        ) -> Result<ListResourcesResult, Error> {
+            Err(Error::TransportClosed)
+        }
+
+        async fn read_resource(
+            &self,
+            _session_id: &str,
+            _uri: &str,
+            _cancellation_token: CancellationToken,
+        ) -> Result<ReadResourceResult, Error> {
+            Err(Error::TransportClosed)
+        }
+
+        async fn list_tools(
+            &self,
+            _session_id: &str,
+            _next_cursor: Option<String>,
+            _cancellation_token: CancellationToken,
+        ) -> Result<ListToolsResult, Error> {
+            use serde_json::json;
+            use std::sync::Arc;
+            Ok(ListToolsResult {
+                tools: vec![
+                    Tool::new(
+                        "db.query".to_string(),
+                        "A tool with a dotted name".to_string(),
+                        Arc::new(json!({}).as_object().unwrap().clone()),
+                    ),
+                    Tool::new(
+                        "db__query".to_string(),
+                        "A sibling with the separator name".to_string(),
+                        Arc::new(json!({}).as_object().unwrap().clone()),
+                    ),
+                ],
+                next_cursor: None,
+                meta: None,
+            })
+        }
+
+        async fn call_tool(
+            &self,
+            _ctx: &ToolCallContext,
+            name: &str,
+            _arguments: Option<JsonObject>,
+            _cancellation_token: CancellationToken,
+        ) -> Result<CallToolResult, Error> {
+            match name {
+                "db.query" | "db__query" => Ok(CallToolResult::success(vec![])),
+                _ => Err(Error::TransportClosed),
+            }
+        }
+
+        async fn list_prompts(
+            &self,
+            _session_id: &str,
+            _next_cursor: Option<String>,
+            _cancellation_token: CancellationToken,
+        ) -> Result<ListPromptsResult, Error> {
+            Err(Error::TransportClosed)
+        }
+
+        async fn get_prompt(
+            &self,
+            _session_id: &str,
+            _name: &str,
+            _arguments: Value,
+            _cancellation_token: CancellationToken,
+        ) -> Result<GetPromptResult, Error> {
+            Err(Error::TransportClosed)
+        }
+
+        async fn subscribe(&self) -> mpsc::Receiver<ServerNotification> {
+            mpsc::channel(1).1
+        }
+    }
+
+    #[tokio::test]
+    async fn test_resolve_tool_recovers_dotted_mangled_name() {
+        let temp_dir = tempfile::tempdir().unwrap();
+        let extension_manager =
+            ExtensionManager::new_without_provider(temp_dir.path().to_path_buf());
+        extension_manager
+            .add_mock_extension("test_client".to_string(), Arc::new(MockClient {}))
+            .await;
+
+        let resolved = extension_manager
+            .resolve_tool("test-session-id", "test_client.tool")
+            .await
+            .expect("mangled dotted name should resolve to the real tool");
+        assert_eq!(resolved.tool_name, "test_client__tool");
+    }
+
+    #[tokio::test]
+    async fn test_resolve_tool_recovers_functions_prefixed_name() {
+        let temp_dir = tempfile::tempdir().unwrap();
+        let extension_manager =
+            ExtensionManager::new_without_provider(temp_dir.path().to_path_buf());
+        extension_manager
+            .add_mock_extension("test_client".to_string(), Arc::new(MockClient {}))
+            .await;
+
+        let resolved = extension_manager
+            .resolve_tool("test-session-id", "functions.test_client__tool")
+            .await
+            .expect("functions-prefixed name should resolve to the real tool");
+        assert_eq!(resolved.tool_name, "test_client__tool");
+    }
+
+    #[tokio::test]
+    async fn test_resolve_tool_exact_dotted_name_never_rewritten() {
+        let temp_dir = tempfile::tempdir().unwrap();
+        let extension_manager =
+            ExtensionManager::new_without_provider(temp_dir.path().to_path_buf());
+        extension_manager
+            .add_mock_extension("dotted".to_string(), Arc::new(MockDottedClient {}))
+            .await;
+
+        let resolved = extension_manager
+            .resolve_tool("test-session-id", "dotted__db.query")
+            .await
+            .expect("exact dotted tool name must resolve");
+        assert_eq!(resolved.tool_name, "dotted__db.query");
+        assert_eq!(resolved.actual_tool_name, "db.query");
+    }
+
+    #[tokio::test]
+    async fn test_resolve_tool_recovers_mangled_separator_with_dotted_tool_name() {
+        let temp_dir = tempfile::tempdir().unwrap();
+        let extension_manager =
+            ExtensionManager::new_without_provider(temp_dir.path().to_path_buf());
+        extension_manager
+            .add_mock_extension("dotted".to_string(), Arc::new(MockDottedClient {}))
+            .await;
+
+        let resolved = extension_manager
+            .resolve_tool("test-session-id", "dotted.db.query")
+            .await
+            .expect("mangled extension separator should resolve");
+        assert_eq!(resolved.tool_name, "dotted__db.query");
+        assert_eq!(resolved.actual_tool_name, "db.query");
+    }
+
+    #[test]
+    fn test_recover_mangled_tool_name() {
+        let tools = ["developer__shell", "platform__search"];
+        assert_eq!(
+            recover_mangled_tool_name("developer.shell", tools.iter().copied()).as_deref(),
+            Some("developer__shell")
+        );
+        assert_eq!(
+            recover_mangled_tool_name("functions.developer__shell", tools.iter().copied())
+                .as_deref(),
+            Some("developer__shell")
+        );
+        assert_eq!(
+            recover_mangled_tool_name("functions.developer.shell", tools.iter().copied())
+                .as_deref(),
+            Some("developer__shell")
+        );
+        assert_eq!(
+            recover_mangled_tool_name("developer shell", tools.iter().copied()),
+            None
+        );
+        assert_eq!(
+            recover_mangled_tool_name("developer__shell!", tools.iter().copied()),
+            None
+        );
+        assert_eq!(
+            recover_mangled_tool_name("nonexistent.tool", tools.iter().copied()),
+            None
+        );
+
+        let dotted_tool = ["dotted__db.query"];
+        assert_eq!(
+            recover_mangled_tool_name("dotted.db.query", dotted_tool.iter().copied()).as_deref(),
+            Some("dotted__db.query")
+        );
+    }
+
     #[test]
     fn test_remove_untrusted_mcp_app_meta_strips_spoofed_payload() {
         let mut result = CallToolResult::success(vec![]);