Merge branch 'main' into main

Author: SoldierSacha

README.md

@@ -31,22 +31,32 @@
     - [Prompts](#prompts)
     - [Images](#images)
     - [Context](#context)
+      - [Getting Context in Functions](#getting-context-in-functions)
+      - [Context Properties and Methods](#context-properties-and-methods)
     - [Completions](#completions)
     - [Elicitation](#elicitation)
     - [Sampling](#sampling)
     - [Logging and Notifications](#logging-and-notifications)
     - [Authentication](#authentication)
     - [FastMCP Properties](#fastmcp-properties)
-    - [Session Properties](#session-properties-and-methods)
+    - [Session Properties and Methods](#session-properties-and-methods)
     - [Request Context Properties](#request-context-properties)
   - [Running Your Server](#running-your-server)
     - [Development Mode](#development-mode)
     - [Claude Desktop Integration](#claude-desktop-integration)
     - [Direct Execution](#direct-execution)
     - [Streamable HTTP Transport](#streamable-http-transport)
+      - [CORS Configuration for Browser-Based Clients](#cors-configuration-for-browser-based-clients)
     - [Mounting to an Existing ASGI Server](#mounting-to-an-existing-asgi-server)
+      - [StreamableHTTP servers](#streamablehttp-servers)
+        - [Basic mounting](#basic-mounting)
+        - [Host-based routing](#host-based-routing)
+        - [Multiple servers with path configuration](#multiple-servers-with-path-configuration)
+        - [Path configuration at initialization](#path-configuration-at-initialization)
+      - [SSE servers](#sse-servers)
   - [Advanced Usage](#advanced-usage)
     - [Low-Level Server](#low-level-server)
+      - [Structured Output Support](#structured-output-support)
     - [Writing MCP Clients](#writing-mcp-clients)
     - [Client Display Utilities](#client-display-utilities)
     - [OAuth Authentication for Clients](#oauth-authentication-for-clients)
@@ -2137,6 +2147,7 @@ MCP servers declare capabilities during initialization:
 
 ## Documentation
 
+- [API Reference](https://modelcontextprotocol.github.io/python-sdk/api/)
 - [Model Context Protocol documentation](https://modelcontextprotocol.io)
 - [Model Context Protocol specification](https://spec.modelcontextprotocol.io)
 - [Officially supported servers](https://github.com/modelcontextprotocol/servers)

src/mcp/server/session.py

@@ -161,6 +161,9 @@ async def _received_request(self, responder: RequestResponder[types.ClientReques
                             )
                         )
                     )
+            case types.PingRequest():
+                # Ping requests are allowed at any time
+                pass
             case _:
                 if self._initialization_state != InitializationState.Initialized:
                     raise RuntimeError("Received request before initialization was complete")

tests/server/test_session.py

@@ -213,3 +213,129 @@ async def mock_client():
 
     assert received_initialized
     assert received_protocol_version == "2024-11-05"
+
+
+@pytest.mark.anyio
+async def test_ping_request_before_initialization():
+    """Test that ping requests are allowed before initialization is complete."""
+    server_to_client_send, server_to_client_receive = anyio.create_memory_object_stream[SessionMessage](1)
+    client_to_server_send, client_to_server_receive = anyio.create_memory_object_stream[SessionMessage | Exception](1)
+
+    ping_response_received = False
+    ping_response_id = None
+
+    async def run_server():
+        async with ServerSession(
+            client_to_server_receive,
+            server_to_client_send,
+            InitializationOptions(
+                server_name="mcp",
+                server_version="0.1.0",
+                capabilities=ServerCapabilities(),
+            ),
+        ) as server_session:
+            async for message in server_session.incoming_messages:
+                if isinstance(message, Exception):
+                    raise message
+
+                # We should receive a ping request before initialization
+                if isinstance(message, RequestResponder) and isinstance(message.request.root, types.PingRequest):
+                    # Respond to the ping
+                    with message:
+                        await message.respond(types.ServerResult(types.EmptyResult()))
+                    return
+
+    async def mock_client():
+        nonlocal ping_response_received, ping_response_id
+
+        # Send ping request before any initialization
+        await client_to_server_send.send(
+            SessionMessage(
+                types.JSONRPCMessage(
+                    types.JSONRPCRequest(
+                        jsonrpc="2.0",
+                        id=42,
+                        method="ping",
+                    )
+                )
+            )
+        )
+
+        # Wait for the ping response
+        ping_response_message = await server_to_client_receive.receive()
+        assert isinstance(ping_response_message.message.root, types.JSONRPCResponse)
+
+        ping_response_received = True
+        ping_response_id = ping_response_message.message.root.id
+
+    async with (
+        client_to_server_send,
+        client_to_server_receive,
+        server_to_client_send,
+        server_to_client_receive,
+        anyio.create_task_group() as tg,
+    ):
+        tg.start_soon(run_server)
+        tg.start_soon(mock_client)
+
+    assert ping_response_received
+    assert ping_response_id == 42
+
+
+@pytest.mark.anyio
+async def test_other_requests_blocked_before_initialization():
+    """Test that non-ping requests are still blocked before initialization."""
+    server_to_client_send, server_to_client_receive = anyio.create_memory_object_stream[SessionMessage](1)
+    client_to_server_send, client_to_server_receive = anyio.create_memory_object_stream[SessionMessage | Exception](1)
+
+    error_response_received = False
+    error_code = None
+
+    async def run_server():
+        async with ServerSession(
+            client_to_server_receive,
+            server_to_client_send,
+            InitializationOptions(
+                server_name="mcp",
+                server_version="0.1.0",
+                capabilities=ServerCapabilities(),
+            ),
+        ):
+            # Server should handle the request and send an error response
+            # No need to process incoming_messages since the error is handled automatically
+            await anyio.sleep(0.1)  # Give time for the request to be processed
+
+    async def mock_client():
+        nonlocal error_response_received, error_code
+
+        # Try to send a non-ping request before initialization
+        await client_to_server_send.send(
+            SessionMessage(
+                types.JSONRPCMessage(
+                    types.JSONRPCRequest(
+                        jsonrpc="2.0",
+                        id=1,
+                        method="prompts/list",
+                    )
+                )
+            )
+        )
+
+        # Wait for the error response
+        error_message = await server_to_client_receive.receive()
+        if isinstance(error_message.message.root, types.JSONRPCError):
+            error_response_received = True
+            error_code = error_message.message.root.error.code
+
+    async with (
+        client_to_server_send,
+        client_to_server_receive,
+        server_to_client_send,
+        server_to_client_receive,
+        anyio.create_task_group() as tg,
+    ):
+        tg.start_soon(run_server)
+        tg.start_soon(mock_client)
+
+    assert error_response_received
+    assert error_code == types.INVALID_PARAMS