Merge branch 'main' into main

Author: ddworken

README.md

@@ -315,27 +315,42 @@ async def long_task(files: list[str], ctx: Context) -> str:
 Authentication can be used by servers that want to expose tools accessing protected resources.
 
 `mcp.server.auth` implements an OAuth 2.0 server interface, which servers can use by
-providing an implementation of the `OAuthServerProvider` protocol.
+providing an implementation of the `OAuthAuthorizationServerProvider` protocol.
 
-```
-mcp = FastMCP("My App",
-        auth_server_provider=MyOAuthServerProvider(),
-        auth=AuthSettings(
-            issuer_url="https://myapp.com",
-            revocation_options=RevocationOptions(
-                enabled=True,
-            ),
-            client_registration_options=ClientRegistrationOptions(
-                enabled=True,
-                valid_scopes=["myscope", "myotherscope"],
-                default_scopes=["myscope"],
-            ),
-            required_scopes=["myscope"],
+```python
+from mcp import FastMCP
+from mcp.server.auth.provider import OAuthAuthorizationServerProvider
+from mcp.server.auth.settings import (
+    AuthSettings,
+    ClientRegistrationOptions,
+    RevocationOptions,
+)
+
+
+class MyOAuthServerProvider(OAuthAuthorizationServerProvider):
+    # See an example on how to implement at `examples/servers/simple-auth`
+    ...
+
+
+mcp = FastMCP(
+    "My App",
+    auth_server_provider=MyOAuthServerProvider(),
+    auth=AuthSettings(
+        issuer_url="https://myapp.com",
+        revocation_options=RevocationOptions(
+            enabled=True,
+        ),
+        client_registration_options=ClientRegistrationOptions(
+            enabled=True,
+            valid_scopes=["myscope", "myotherscope"],
+            default_scopes=["myscope"],
         ),
+        required_scopes=["myscope"],
+    ),
 )
 ```
 
-See [OAuthServerProvider](src/mcp/server/auth/provider.py) for more details.
+See [OAuthAuthorizationServerProvider](src/mcp/server/auth/provider.py) for more details.
 
 ## Running Your Server
 
@@ -462,15 +477,12 @@ For low level server with Streamable HTTP implementations, see:
 - Stateful server: [`examples/servers/simple-streamablehttp/`](examples/servers/simple-streamablehttp/)
 - Stateless server: [`examples/servers/simple-streamablehttp-stateless/`](examples/servers/simple-streamablehttp-stateless/)
 
-
-
 The streamable HTTP transport supports:
 - Stateful and stateless operation modes
 - Resumability with event stores
-- JSON or SSE response formats  
+- JSON or SSE response formats
 - Better scalability for multi-node deployments
 
-
 ### Mounting to an Existing ASGI Server
 
 > **Note**: SSE transport is being superseded by [Streamable HTTP transport](https://modelcontextprotocol.io/specification/2025-03-26/basic/transports#streamable-http).

src/mcp/client/session.py

@@ -116,12 +116,18 @@ def __init__(
         self._message_handler = message_handler or _default_message_handler
 
     async def initialize(self) -> types.InitializeResult:
-        sampling = types.SamplingCapability()
-        roots = types.RootsCapability(
+        sampling = (
+            types.SamplingCapability()
+            if self._sampling_callback is not _default_sampling_callback
+            else None
+        )
+        roots = (
             # TODO: Should this be based on whether we
             # _will_ send notifications, or only whether
             # they're supported?
-            listChanged=True,
+            types.RootsCapability(listChanged=True)
+            if self._list_roots_callback is not _default_list_roots_callback
+            else None
         )
 
         result = await self.send_request(

src/mcp/client/stdio/__init__.py

@@ -108,20 +108,28 @@ async def stdio_client(server: StdioServerParameters, errlog: TextIO = sys.stder
     read_stream_writer, read_stream = anyio.create_memory_object_stream(0)
     write_stream, write_stream_reader = anyio.create_memory_object_stream(0)
 
-    command = _get_executable_command(server.command)
-
-    # Open process with stderr piped for capture
-    process = await _create_platform_compatible_process(
-        command=command,
-        args=server.args,
-        env=(
-            {**get_default_environment(), **server.env}
-            if server.env is not None
-            else get_default_environment()
-        ),
-        errlog=errlog,
-        cwd=server.cwd,
-    )
+    try:
+        command = _get_executable_command(server.command)
+
+        # Open process with stderr piped for capture
+        process = await _create_platform_compatible_process(
+            command=command,
+            args=server.args,
+            env=(
+                {**get_default_environment(), **server.env}
+                if server.env is not None
+                else get_default_environment()
+            ),
+            errlog=errlog,
+            cwd=server.cwd,
+        )
+    except OSError:
+        # Clean up streams if process creation fails
+        await read_stream.aclose()
+        await write_stream.aclose()
+        await read_stream_writer.aclose()
+        await write_stream_reader.aclose()
+        raise
 
     async def stdout_reader():
         assert process.stdout, "Opened process is missing stdout"
@@ -177,12 +185,18 @@ async def stdin_writer():
             yield read_stream, write_stream
         finally:
             # Clean up process to prevent any dangling orphaned processes
-            if sys.platform == "win32":
-                await terminate_windows_process(process)
-            else:
-                process.terminate()
+            try:
+                if sys.platform == "win32":
+                    await terminate_windows_process(process)
+                else:
+                    process.terminate()
+            except ProcessLookupError:
+                # Process already exited, which is fine
+                pass
             await read_stream.aclose()
             await write_stream.aclose()
+            await read_stream_writer.aclose()
+            await write_stream_reader.aclose()
 
 
 def _get_executable_command(command: str) -> str:

src/mcp/server/lowlevel/server.py

@@ -147,7 +147,7 @@ def __init__(
         }
         self.notification_handlers: dict[type, Callable[..., Awaitable[None]]] = {}
         self.notification_options = NotificationOptions()
-        logger.debug(f"Initializing server '{name}'")
+        logger.debug("Initializing server %r", name)
 
     def create_initialization_options(
         self,
@@ -510,7 +510,7 @@ async def run(
 
             async with anyio.create_task_group() as tg:
                 async for message in session.incoming_messages:
-                    logger.debug(f"Received message: {message}")
+                    logger.debug("Received message: %s", message)
 
                     tg.start_soon(
                         self._handle_message,
@@ -543,7 +543,9 @@ async def _handle_message(
                     await self._handle_notification(notify)
 
             for warning in w:
-                logger.info(f"Warning: {warning.category.__name__}: {warning.message}")
+                logger.info(
+                    "Warning: %s: %s", warning.category.__name__, warning.message
+                )
 
     async def _handle_request(
         self,
@@ -553,10 +555,9 @@ async def _handle_request(
         lifespan_context: LifespanResultT,
         raise_exceptions: bool,
     ):
-        logger.info(f"Processing request of type {type(req).__name__}")
-        if type(req) in self.request_handlers:
-            handler = self.request_handlers[type(req)]
-            logger.debug(f"Dispatching request of type {type(req).__name__}")
+        logger.info("Processing request of type %s", type(req).__name__)
+        if handler := self.request_handlers.get(type(req)):  # type: ignore
+            logger.debug("Dispatching request of type %s", type(req).__name__)
 
             token = None
             try:
@@ -602,16 +603,13 @@ async def _handle_request(
         logger.debug("Response sent")
 
     async def _handle_notification(self, notify: Any):
-        if type(notify) in self.notification_handlers:
-            assert type(notify) in self.notification_handlers
-
-            handler = self.notification_handlers[type(notify)]
-            logger.debug(f"Dispatching notification of type {type(notify).__name__}")
+        if handler := self.notification_handlers.get(type(notify)):  # type: ignore
+            logger.debug("Dispatching notification of type %s", type(notify).__name__)
 
             try:
                 await handler(notify)
-            except Exception as err:
-                logger.error(f"Uncaught exception in notification handler: {err}")
+            except Exception:
+                logger.exception("Uncaught exception in notification handler")
 
 
 async def _ping_handler(request: types.PingRequest) -> types.ServerResult:

src/mcp/server/streamable_http.py

@@ -397,7 +397,8 @@ async def _handle_post_request(
                 await response(scope, receive, send)
 
                 # Process the message after sending the response
-                session_message = SessionMessage(message)
+                metadata = ServerMessageMetadata(request_context=request)
+                session_message = SessionMessage(message, metadata=metadata)
                 await writer.send(session_message)
 
                 return
@@ -412,7 +413,8 @@ async def _handle_post_request(
 
             if self.is_json_response_enabled:
                 # Process the message
-                session_message = SessionMessage(message)
+                metadata = ServerMessageMetadata(request_context=request)
+                session_message = SessionMessage(message, metadata=metadata)
                 await writer.send(session_message)
                 try:
                     # Process messages from the request-specific stream
@@ -511,7 +513,8 @@ async def sse_writer():
                     async with anyio.create_task_group() as tg:
                         tg.start_soon(response, scope, receive, send)
                         # Then send the message to be processed by the server
-                        session_message = SessionMessage(message)
+                        metadata = ServerMessageMetadata(request_context=request)
+                        session_message = SessionMessage(message, metadata=metadata)
                         await writer.send(session_message)
                 except Exception:
                     logger.exception("SSE response error")

src/mcp/types.py

@@ -218,7 +218,7 @@ class RootsCapability(BaseModel):
 
 
 class SamplingCapability(BaseModel):
-    """Capability for logging operations."""
+    """Capability for sampling operations."""
 
     model_config = ConfigDict(extra="allow")