Add get_server_capabilities() to ClientSession (#1588)

src/mcp/client/session.py

@@ -134,6 +134,7 @@ class ClientSession(
         self._logging_callback = logging_callback or _default_logging_callback
         self._message_handler = message_handler or _default_message_handler
         self._tool_output_schemas: dict[str, dict[str, Any] | None] = {}
+        self._server_capabilities: types.ServerCapabilities | None = None
 
     async def initialize(self) -> types.InitializeResult:
         sampling = types.SamplingCapability() if self._sampling_callback is not _default_sampling_callback else None
@@ -170,10 +171,19 @@ class ClientSession(
         if result.protocolVersion not in SUPPORTED_PROTOCOL_VERSIONS:
             raise RuntimeError(f"Unsupported protocol version from the server: {result.protocolVersion}")
 
+        self._server_capabilities = result.capabilities
+
         await self.send_notification(types.ClientNotification(types.InitializedNotification()))
 
         return result
 
+    def get_server_capabilities(self) -> types.ServerCapabilities | None:
+        """Return the server capabilities received during initialization.
+
+        Returns None if the session has not been initialized yet.
+        """
+        return self._server_capabilities
+
     async def send_ping(self) -> types.EmptyResult:
         """Send a ping request."""
         return await self.send_request(