Expose server_info in MCPServer (#3055)

Author: Whadup

pydantic_ai_slim/pydantic_ai/mcp.py

@@ -112,6 +112,7 @@ class MCPServer(AbstractToolset[Any], ABC):
     _client: ClientSession
     _read_stream: MemoryObjectReceiveStream[SessionMessage | Exception]
     _write_stream: MemoryObjectSendStream[SessionMessage]
+    _server_info: mcp_types.Implementation
 
     def __init__(
         self,
@@ -177,6 +178,15 @@ def label(self) -> str:
     def tool_name_conflict_hint(self) -> str:
         return 'Set the `tool_prefix` attribute to avoid name conflicts.'
 
+    @property
+    def server_info(self) -> mcp_types.Implementation:
+        """Access the information send by the MCP server during initialization."""
+        if getattr(self, '_server_info', None) is None:
+            raise AttributeError(
+                f'The `{self.__class__.__name__}.server_info` is only instantiated after initialization.'
+            )
+        return self._server_info
+
     async def list_tools(self) -> list[mcp_types.Tool]:
         """Retrieve tools that are currently active on the server.
 
@@ -312,8 +322,8 @@ async def __aenter__(self) -> Self:
                     self._client = await exit_stack.enter_async_context(client)
 
                     with anyio.fail_after(self.timeout):
-                        await self._client.initialize()
-
+                        result = await self._client.initialize()
+                        self._server_info = result.serverInfo
                         if log_level := self.log_level:
                             await self._client.set_logging_level(log_level)
 

tests/test_mcp.py

@@ -1474,3 +1474,13 @@ def test_load_mcp_servers(tmp_path: Path):
 
     with pytest.raises(FileNotFoundError):
         load_mcp_servers(tmp_path / 'does_not_exist.json')
+
+
+async def test_server_info(mcp_server: MCPServerStdio) -> None:
+    with pytest.raises(
+        AttributeError, match='The `MCPServerStdio.server_info` is only instantiated after initialization.'
+    ):
+        mcp_server.server_info
+    async with mcp_server:
+        assert mcp_server.server_info is not None
+        assert mcp_server.server_info.name == 'Pydantic AI MCP Server'