Merge branch 'modelcontextprotocol:main' into modelcontextprotocol#552

Author: DanielAvdar

README.md

@@ -318,7 +318,7 @@ providing an implementation of the `OAuthServerProvider` protocol.
 
 ```
 mcp = FastMCP("My App",
-        auth_provider=MyOAuthServerProvider(),
+        auth_server_provider=MyOAuthServerProvider(),
         auth=AuthSettings(
             issuer_url="https://myapp.com",
             revocation_options=RevocationOptions(
@@ -387,6 +387,8 @@ python server.py
 mcp run server.py
 ```
 
+Note that `mcp run` or `mcp dev` only supports server using FastMCP and not the low-level server variant.
+
 ### Streamable HTTP Transport
 
 > **Note**: Streamable HTTP transport is superseding SSE transport for production deployments.
@@ -426,7 +428,7 @@ mcp = FastMCP(name="MathServer", stateless_http=True)
 
 
 @mcp.tool(description="A simple add tool")
-def add_two(n: int) -> str:
+def add_two(n: int) -> int:
     return n + 2
 ```
 
@@ -462,6 +464,8 @@ The streamable HTTP transport supports:
 
 > **Note**: SSE transport is being superseded by [Streamable HTTP transport](https://modelcontextprotocol.io/specification/2025-03-26/basic/transports#streamable-http).
 
+By default, SSE servers are mounted at `/sse` and Streamable HTTP servers are mounted at `/mcp`. You can customize these paths using the methods described below.
+
 You can mount the SSE server to an existing ASGI server using the `sse_app` method. This allows you to integrate the SSE server with other ASGI applications.
 
 ```python
@@ -617,7 +621,7 @@ server = Server("example-server", lifespan=server_lifespan)
 # Access lifespan context in handlers
 @server.call_tool()
 async def query_db(name: str, arguments: dict) -> list:
-    ctx = server.request_context
+    ctx = server.get_context()
     db = ctx.lifespan_context["db"]
     return await db.query(arguments["query"])
 ```
@@ -692,6 +696,8 @@ if __name__ == "__main__":
     asyncio.run(run())
 ```
 
+Caution: The `mcp run` and `mcp dev` tool doesn't support low-level server.
+
 ### Writing MCP Clients
 
 The SDK provides a high-level client interface for connecting to MCP servers using various [transports](https://modelcontextprotocol.io/specification/2025-03-26/basic/transports):

examples/clients/simple-chatbot/README.MD

@@ -25,6 +25,7 @@ This example demonstrates how to integrate the Model Context Protocol (MCP) into
    ```plaintext
    LLM_API_KEY=your_api_key_here
    ```
+   **Note:** The current implementation is configured to use the Groq API endpoint (`https://api.groq.com/openai/v1/chat/completions`) with the `llama-3.2-90b-vision-preview` model. If you plan to use a different LLM provider, you'll need to modify the `LLMClient` class in `main.py` to use the appropriate endpoint URL and model parameters.
 
 3. **Configure servers:**
 

examples/servers/simple-auth/README.md

@@ -44,6 +44,31 @@ uv run mcp-simple-auth
 
 The server will start on `http://localhost:8000`.
 
+### Transport Options
+
+This server supports multiple transport protocols that can run on the same port:
+
+#### SSE (Server-Sent Events) - Default
+```bash
+uv run mcp-simple-auth
+# or explicitly:
+uv run mcp-simple-auth --transport sse
+```
+
+SSE transport provides endpoint:
+- `/sse`
+
+#### Streamable HTTP
+```bash
+uv run mcp-simple-auth --transport streamable-http
+```
+
+Streamable HTTP transport provides endpoint:
+- `/mcp`
+
+
+This ensures backward compatibility without needing multiple server instances. When using SSE transport (`--transport sse`), only the `/sse` endpoint is available.
+
 ## Available Tool
 
 ### get_user_profile
@@ -61,5 +86,6 @@ If the server fails to start, check:
 1. Environment variables `MCP_GITHUB_GITHUB_CLIENT_ID` and `MCP_GITHUB_GITHUB_CLIENT_SECRET` are set
 2. The GitHub OAuth app callback URL matches `http://localhost:8000/github/callback`
 3. No other service is using port 8000
+4. The transport specified is valid (`sse` or `streamable-http`)
 
 You can use [Inspector](https://github.com/modelcontextprotocol/inspector) to test Auth

examples/servers/simple-auth/mcp_simple_auth/server.py

@@ -3,7 +3,7 @@
 import logging
 import secrets
 import time
-from typing import Any
+from typing import Any, Literal
 
 import click
 from pydantic import AnyHttpUrl
@@ -347,7 +347,13 @@ async def get_user_profile() -> dict[str, Any]:
 @click.command()
 @click.option("--port", default=8000, help="Port to listen on")
 @click.option("--host", default="localhost", help="Host to bind to")
-def main(port: int, host: str) -> int:
+@click.option(
+    "--transport",
+    default="sse",
+    type=click.Choice(["sse", "streamable-http"]),
+    help="Transport protocol to use ('sse' or 'streamable-http')",
+)
+def main(port: int, host: str, transport: Literal["sse", "streamable-http"]) -> int:
     """Run the simple GitHub MCP server."""
     logging.basicConfig(level=logging.INFO)
 
@@ -364,5 +370,6 @@ def main(port: int, host: str) -> int:
         return 1
 
     mcp_server = create_simple_mcp_server(settings)
-    mcp_server.run(transport="sse")
+    logger.info(f"Starting server with {transport} transport")
+    mcp_server.run(transport=transport)
     return 0

src/mcp/__init__.py

@@ -1,4 +1,5 @@
 from .client.session import ClientSession
+from .client.session_group import ClientSessionGroup
 from .client.stdio import StdioServerParameters, stdio_client
 from .server.session import ServerSession
 from .server.stdio import stdio_server
@@ -63,6 +64,7 @@
     "ClientRequest",
     "ClientResult",
     "ClientSession",
+    "ClientSessionGroup",
     "CreateMessageRequest",
     "CreateMessageResult",
     "ErrorData",

src/mcp/cli/claude.py

@@ -31,6 +31,7 @@ def get_claude_config_path() -> Path | None:
         return path
     return None
 
+
 def get_uv_path() -> str:
     """Get the full path to the uv executable."""
     uv_path = shutil.which("uv")
@@ -42,6 +43,7 @@ def get_uv_path() -> str:
         return "uv"  # Fall back to just "uv" if not found
     return uv_path
 
+
 def update_claude_config(
     file_spec: str,
     server_name: str,

src/mcp/cli/cli.py

@@ -6,7 +6,10 @@
 import subprocess
 import sys
 from pathlib import Path
-from typing import Annotated
+from typing import Annotated, Any
+
+from mcp.server import FastMCP
+from mcp.server import Server as LowLevelServer
 
 try:
     import typer
@@ -141,17 +144,48 @@ def _import_server(file: Path, server_object: str | None = None):
     module = importlib.util.module_from_spec(spec)
     spec.loader.exec_module(module)
 
+    def _check_server_object(server_object: Any, object_name: str):
+        """Helper function to check that the server object is supported
+
+        Args:
+            server_object: The server object to check.
+
+        Returns:
+            True if it's supported.
+        """
+        if not isinstance(server_object, FastMCP):
+            logger.error(
+                f"The server object {object_name} is of type "
+                f"{type(server_object)} (expecting {FastMCP})."
+            )
+            if isinstance(server_object, LowLevelServer):
+                logger.warning(
+                    "Note that only FastMCP server is supported. Low level "
+                    "Server class is not yet supported."
+                )
+            return False
+        return True
+
     # If no object specified, try common server names
     if not server_object:
         # Look for the most common server object names
         for name in ["mcp", "server", "app"]:
             if hasattr(module, name):
+                if not _check_server_object(getattr(module, name), f"{file}:{name}"):
+                    logger.error(
+                        f"Ignoring object '{file}:{name}' as it's not a valid "
+                        "server object"
+                    )
+                    continue
                 return getattr(module, name)
 
         logger.error(
             f"No server object found in {file}. Please either:\n"
             "1. Use a standard variable name (mcp, server, or app)\n"
-            "2. Specify the object name with file:object syntax",
+            "2. Specify the object name with file:object syntax"
+            "3. If the server creates the FastMCP object within main() "
+            "   or another function, refactor the FastMCP object to be a "
+            "   global variable named mcp, server, or app.",
             extra={"file": str(file)},
         )
         sys.exit(1)
@@ -179,6 +213,9 @@ def _import_server(file: Path, server_object: str | None = None):
         )
         sys.exit(1)
 
+    if not _check_server_object(server, server_object):
+        sys.exit(1)
+
     return server