Add QA discoverability to MCP instructions and localhost guard for cloud browsers (#4984)

skyvern/cli/mcp_tools/_localhost.py

@@ -0,0 +1,25 @@
+"""Localhost URL detection for cloud browser sessions."""
+
+from __future__ import annotations
+
+from urllib.parse import urlparse
+
+_LOCALHOST_HOSTNAMES = frozenset(
+    {
+        "localhost",
+        "127.0.0.1",
+        "0.0.0.0",  # noqa: S104 — detection, not binding
+        "::1",
+        "[::1]",
+    }
+)
+
+
+def is_localhost_url(url: str) -> bool:
+    """Return True if *url* points to a loopback address."""
+    try:
+        parsed = urlparse(url)
+        hostname = (parsed.hostname or "").lower()
+        return hostname in _LOCALHOST_HOSTNAMES
+    except Exception:
+        return False