feat(mcp): raise default tool-call timeout 120s -> 300s

Port from openai/codex#28234. Long-running MCP tools (web fetches,
sandboxed builds, deep-research servers) routinely exceed 120s, causing
spurious timeout failures. Codex bumped its default MCP tool timeout from
120 to 300 for the same reason.

- _DEFAULT_TOOL_TIMEOUT 120 -> 300 in tools/mcp_tool.py (per-server
  'timeout' config override unchanged)
- update test_default_timeout assertion
- document the default in mcp-config-reference.md

tests/tools/test_mcp_tool.py

@@ -1884,7 +1884,7 @@ class TestConfigurableTimeouts:
 
         server = MCPServerTask("test_srv")
         assert server.tool_timeout == _DEFAULT_TOOL_TIMEOUT
-        assert server.tool_timeout == 120
+        assert server.tool_timeout == 300
 
     def test_custom_timeout(self):
         """Server with timeout=180 in config gets 180."""

tools/mcp_tool.py

@@ -17,7 +17,7 @@ Example config::
         command: "npx"
         args: ["-y", "@modelcontextprotocol/server-filesystem", "/tmp"]
         env: {}
-        timeout: 120         # per-tool-call timeout in seconds (default: 120)
+        timeout: 120         # per-tool-call timeout in seconds (default: 300)
         connect_timeout: 60  # initial connection timeout (default: 60)
       github:
         command: "npx"
@@ -258,7 +258,7 @@ if _MCP_AVAILABLE and not _MCP_MESSAGE_HANDLER_SUPPORTED:
 # Constants
 # ---------------------------------------------------------------------------
 
-_DEFAULT_TOOL_TIMEOUT = 120      # seconds for tool calls
+_DEFAULT_TOOL_TIMEOUT = 300      # seconds for tool calls
 _DEFAULT_CONNECT_TIMEOUT = 60    # seconds for initial connection per server
 _MAX_RECONNECT_RETRIES = 5
 _MAX_INITIAL_CONNECT_RETRIES = 3 # retries for the very first connection attempt

website/docs/reference/mcp-config-reference.md

@@ -54,8 +54,8 @@ mcp_servers:
 | `client_cert` | string or list | HTTP | mTLS client certificate. String = path to a PEM file containing cert + key. List `[cert, key]` = separate files. List `[cert, key, password]` = encrypted key |
 | `client_key` | string | HTTP | Path to the client private key, when `client_cert` is a string and the key is in a separate file |
 | `enabled` | bool | both | Skip the server entirely when false |
-| `timeout` | number | both | Tool call timeout |
-| `connect_timeout` | number | both | Initial connection timeout |
+| `timeout` | number | both | Tool call timeout in seconds (default: `300`) |
+| `connect_timeout` | number | both | Initial connection timeout in seconds (default: `60`) |
 | `supports_parallel_tool_calls` | bool | both | Allow tools from this server to run concurrently |
 | `tools` | mapping | both | Filtering and utility-tool policy |
 | `auth` | string | HTTP | Authentication method. Set to `oauth` to enable OAuth 2.1 with PKCE |