diff --git a/docs/migration.md b/docs/migration.md index 7cf032553..dd6a7a18f 100644 --- a/docs/migration.md +++ b/docs/migration.md @@ -169,6 +169,30 @@ result = await session.list_resources(params=PaginatedRequestParams(cursor="next result = await session.list_tools(params=PaginatedRequestParams(cursor="next_page_token")) ``` +### `ClientSession.get_server_capabilities()` replaced by `initialize_result` property + +`ClientSession` now stores the full `InitializeResult` via an `initialize_result` property. This provides access to `server_info`, `capabilities`, `instructions`, and the negotiated `protocol_version` through a single property. The `get_server_capabilities()` method has been removed. + +**Before (v1):** + +```python +capabilities = session.get_server_capabilities() +# server_info, instructions, protocol_version were not stored — had to capture initialize() return value +``` + +**After (v2):** + +```python +result = session.initialize_result +if result is not None: + capabilities = result.capabilities + server_info = result.server_info + instructions = result.instructions + version = result.protocol_version +``` + +The high-level `Client.initialize_result` returns the same `InitializeResult` but is non-nullable — initialization is guaranteed inside the context manager, so no `None` check is needed. This replaces v1's `Client.server_capabilities`; use `client.initialize_result.capabilities` instead. + ### `McpError` renamed to `MCPError` The `McpError` exception class has been renamed to `MCPError` for consistent naming with the MCP acronym style used throughout the SDK. diff --git a/src/mcp/client/client.py b/src/mcp/client/client.py index 7dc67c584..34d6a360f 100644 --- a/src/mcp/client/client.py +++ b/src/mcp/client/client.py @@ -19,6 +19,7 @@ EmptyResult, GetPromptResult, Implementation, + InitializeResult, ListPromptsResult, ListResourcesResult, ListResourceTemplatesResult, @@ -29,7 +30,6 @@ ReadResourceResult, RequestParamsMeta, ResourceTemplateReference, - ServerCapabilities, ) @@ -155,9 +155,16 @@ def session(self) -> ClientSession: return self._session @property - def server_capabilities(self) -> ServerCapabilities | None: - """The server capabilities received during initialization, or None if not yet initialized.""" - return self.session.get_server_capabilities() + def initialize_result(self) -> InitializeResult: + """The server's InitializeResult. + + Contains server_info, capabilities, instructions, and the negotiated protocol_version. + Raises RuntimeError if accessed outside the context manager. + """ + result = self.session.initialize_result + if result is None: # pragma: no cover + raise RuntimeError("Client must be used within an async context manager") + return result async def send_ping(self, *, meta: RequestParamsMeta | None = None) -> EmptyResult: """Send a ping request to the server.""" diff --git a/src/mcp/client/session.py b/src/mcp/client/session.py index a0ca751bd..7c964a334 100644 --- a/src/mcp/client/session.py +++ b/src/mcp/client/session.py @@ -131,7 +131,7 @@ def __init__( 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 + self._initialize_result: types.InitializeResult | None = None self._experimental_features: ExperimentalClientFeatures | None = None # Experimental: Task handlers (use defaults if not provided) @@ -185,18 +185,19 @@ async def initialize(self) -> types.InitializeResult: if result.protocol_version not in SUPPORTED_PROTOCOL_VERSIONS: raise RuntimeError(f"Unsupported protocol version from the server: {result.protocol_version}") - self._server_capabilities = result.capabilities + self._initialize_result = result await self.send_notification(types.InitializedNotification()) return result - def get_server_capabilities(self) -> types.ServerCapabilities | None: - """Return the server capabilities received during initialization. + @property + def initialize_result(self) -> types.InitializeResult | None: + """The server's InitializeResult. None until initialize() has been called. - Returns None if the session has not been initialized yet. + Contains server_info, capabilities, instructions, and the negotiated protocol_version. """ - return self._server_capabilities + return self._initialize_result @property def experimental(self) -> ExperimentalClientFeatures: diff --git a/tests/client/test_client.py b/tests/client/test_client.py index 3bdd30570..18368e6bb 100644 --- a/tests/client/test_client.py +++ b/tests/client/test_client.py @@ -99,7 +99,7 @@ def greeting_prompt(name: str) -> str: async def test_client_is_initialized(app: MCPServer): """Test that the client is initialized after entering context.""" async with Client(app) as client: - assert client.server_capabilities == snapshot( + assert client.initialize_result.capabilities == snapshot( ServerCapabilities( experimental={}, prompts=PromptsCapability(list_changed=False), @@ -107,6 +107,7 @@ async def test_client_is_initialized(app: MCPServer): tools=ToolsCapability(list_changed=False), ) ) + assert client.initialize_result.server_info.name == "test" async def test_client_with_simple_server(simple_server: Server): diff --git a/tests/client/test_session.py b/tests/client/test_session.py index d6d13e273..f25c964f0 100644 --- a/tests/client/test_session.py +++ b/tests/client/test_session.py @@ -540,8 +540,8 @@ async def mock_server(): @pytest.mark.anyio -async def test_get_server_capabilities(): - """Test that get_server_capabilities returns None before init and capabilities after""" +async def test_initialize_result(): + """Test that initialize_result is None before init and contains the full result after.""" client_to_server_send, client_to_server_receive = anyio.create_memory_object_stream[SessionMessage](1) server_to_client_send, server_to_client_receive = anyio.create_memory_object_stream[SessionMessage](1) @@ -551,6 +551,8 @@ async def test_get_server_capabilities(): resources=types.ResourcesCapability(subscribe=True, list_changed=True), tools=types.ToolsCapability(list_changed=False), ) + expected_server_info = Implementation(name="mock-server", version="0.1.0") + expected_instructions = "Use the tools wisely." async def mock_server(): session_message = await client_to_server_receive.receive() @@ -564,7 +566,8 @@ async def mock_server(): result = InitializeResult( protocol_version=LATEST_PROTOCOL_VERSION, capabilities=expected_capabilities, - server_info=Implementation(name="mock-server", version="0.1.0"), + server_info=expected_server_info, + instructions=expected_instructions, ) async with server_to_client_send: @@ -590,21 +593,17 @@ async def mock_server(): server_to_client_send, server_to_client_receive, ): - assert session.get_server_capabilities() is None + assert session.initialize_result is None tg.start_soon(mock_server) await session.initialize() - capabilities = session.get_server_capabilities() - assert capabilities is not None - assert capabilities == expected_capabilities - assert capabilities.logging is not None - assert capabilities.prompts is not None - assert capabilities.prompts.list_changed is True - assert capabilities.resources is not None - assert capabilities.resources.subscribe is True - assert capabilities.tools is not None - assert capabilities.tools.list_changed is False + result = session.initialize_result + assert result is not None + assert result.server_info == expected_server_info + assert result.capabilities == expected_capabilities + assert result.instructions == expected_instructions + assert result.protocol_version == LATEST_PROTOCOL_VERSION @pytest.mark.anyio diff --git a/tests/client/transports/test_memory.py b/tests/client/transports/test_memory.py index 47be3e208..c8fc41fd5 100644 --- a/tests/client/transports/test_memory.py +++ b/tests/client/transports/test_memory.py @@ -69,7 +69,7 @@ async def test_with_mcpserver(mcpserver_server: MCPServer): async def test_server_is_running(mcpserver_server: MCPServer): """Test that the server is running and responding to requests.""" async with Client(mcpserver_server) as client: - assert client.server_capabilities is not None + assert client.initialize_result.capabilities.tools is not None async def test_list_tools(mcpserver_server: MCPServer): diff --git a/tests/server/mcpserver/test_integration.py b/tests/server/mcpserver/test_integration.py index 90e333b77..f71c0574c 100644 --- a/tests/server/mcpserver/test_integration.py +++ b/tests/server/mcpserver/test_integration.py @@ -109,8 +109,7 @@ async def elicitation_callback(context: RequestContext[ClientSession], params: E async def test_basic_tools() -> None: """Test basic tool functionality.""" async with Client(basic_tool.mcp) as client: - assert client.server_capabilities is not None - assert client.server_capabilities.tools is not None + assert client.initialize_result.capabilities.tools is not None # Test sum tool tool_result = await client.call_tool("sum", {"a": 5, "b": 3}) @@ -128,8 +127,7 @@ async def test_basic_tools() -> None: async def test_basic_resources() -> None: """Test basic resource functionality.""" async with Client(basic_resource.mcp) as client: - assert client.server_capabilities is not None - assert client.server_capabilities.resources is not None + assert client.initialize_result.capabilities.resources is not None # Test document resource doc_content = await client.read_resource("file://documents/readme") @@ -151,8 +149,7 @@ async def test_basic_resources() -> None: async def test_basic_prompts() -> None: """Test basic prompt functionality.""" async with Client(basic_prompt.mcp) as client: - assert client.server_capabilities is not None - assert client.server_capabilities.prompts is not None + assert client.initialize_result.capabilities.prompts is not None # Test review_code prompt prompts = await client.list_prompts() @@ -223,8 +220,7 @@ async def progress_callback(progress: float, total: float | None, message: str | async def test_sampling() -> None: """Test sampling (LLM interaction) functionality.""" async with Client(sampling.mcp, sampling_callback=sampling_callback) as client: - assert client.server_capabilities is not None - assert client.server_capabilities.tools is not None + assert client.initialize_result.capabilities.tools is not None # Test sampling tool sampling_result = await client.call_tool("generate_poem", {"topic": "nature"}) @@ -294,9 +290,8 @@ async def message_handler(message: RequestResponder[ServerRequest, ClientResult] async def test_completion() -> None: """Test completion (autocomplete) functionality.""" async with Client(completion.mcp) as client: - assert client.server_capabilities is not None - assert client.server_capabilities.resources is not None - assert client.server_capabilities.prompts is not None + assert client.initialize_result.capabilities.resources is not None + assert client.initialize_result.capabilities.prompts is not None # Test resource completion completion_result = await client.complete(