docs: Add StreamableHTTP path configuration documentation

- Add dedicated StreamableHTTP servers section in README
- Explain default /mcp path behavior and configuration options
- Add examples showing how to mount at custom paths
- Create new snippet for StreamableHTTP mounting patterns
- Update existing Starlette mount snippet with clarifying comments

This helps users understand and avoid the double-path issue when
mounting StreamableHTTP servers (e.g., /mcp/mcp instead of /mcp).

Author: felixweinberger

README.md

@@ -1011,38 +1011,44 @@ For more information on mounting applications in Starlette, see the [Starlette d
 
 You can mount the StreamableHTTP server to an existing ASGI server using the `streamable_http_app` method. This allows you to integrate the StreamableHTTP server with other ASGI applications.
 
+<!-- snippet-source examples/snippets/servers/streamable_http_mounting.py -->
 ```python
 from starlette.applications import Starlette
-from starlette.routing import Mount, Host
-from mcp.server.fastmcp import FastMCP
+from starlette.routing import Host, Mount
 
+from mcp.server.fastmcp import FastMCP
 
+# Basic example - mounting at root
 mcp = FastMCP("My App")
 
+
+@mcp.tool()
+def hello() -> str:
+    """A simple hello tool"""
+    return "Hello from MCP!"
+
+
 # Mount the StreamableHTTP server to the existing ASGI server
 app = Starlette(
     routes=[
-        Mount('/', app=mcp.streamable_http_app()),
+        Mount("/", app=mcp.streamable_http_app()),
     ]
 )
 
 # or dynamically mount as host
-app.router.routes.append(Host('mcp.acme.corp', app=mcp.streamable_http_app()))
+app.router.routes.append(Host("mcp.acme.corp", app=mcp.streamable_http_app()))
 ```
 
 When mounting StreamableHTTP servers, be aware that the server's `streamable_http_path` setting (default: `/mcp`) is relative to where you mount the app. For example:
 
 ```python
-from starlette.applications import Starlette
-from starlette.routing import Mount
-from mcp.server.fastmcp import FastMCP
-
+# Advanced example - multiple servers with path configuration
 # Create multiple MCP servers
 api_mcp = FastMCP("API Server")
 chat_mcp = FastMCP("Chat Server")
 
 # Default behavior: endpoints will be at /api/mcp and /chat/mcp
-app = Starlette(
+default_app = Starlette(
     routes=[
         Mount("/api", app=api_mcp.streamable_http_app()),
         Mount("/chat", app=chat_mcp.streamable_http_app()),
@@ -1058,6 +1064,9 @@ chat_mcp.settings.streamable_http_path = "/"
 mcp_at_root = FastMCP("My Server", streamable_http_path="/")
 ```
 
+_Full example: [examples/snippets/servers/streamable_http_mounting.py](https://github.com/modelcontextprotocol/python-sdk/blob/main/examples/snippets/servers/streamable_http_mounting.py)_
+<!-- /snippet-source -->
+
 #### SSE servers
 
 > **Note**: SSE transport is being superseded by [Streamable HTTP transport](https://modelcontextprotocol.io/specification/2025-03-26/basic/transports#streamable-http).

examples/snippets/servers/streamable_http_mounting.py

@@ -0,0 +1,72 @@
+"""
+Example showing how to mount StreamableHTTP servers in Starlette applications.
+
+Run from the repository root:
+    uvicorn examples.snippets.servers.streamable_http_mounting:app --reload
+"""
+
+from starlette.applications import Starlette
+from starlette.routing import Host, Mount
+
+from mcp.server.fastmcp import FastMCP
+
+# Basic example - mounting at root
+mcp = FastMCP("My App")
+
+
+@mcp.tool()
+def hello() -> str:
+    """A simple hello tool"""
+    return "Hello from MCP!"
+
+
+# Mount the StreamableHTTP server to the existing ASGI server
+app = Starlette(
+    routes=[
+        Mount("/", app=mcp.streamable_http_app()),
+    ]
+)
+
+# or dynamically mount as host
+app.router.routes.append(Host("mcp.acme.corp", app=mcp.streamable_http_app()))
+
+# Advanced example - multiple servers with path configuration
+# Create multiple MCP servers
+api_mcp = FastMCP("API Server")
+chat_mcp = FastMCP("Chat Server")
+
+
+@api_mcp.tool()
+def api_status() -> str:
+    """Get API status"""
+    return "API is running"
+
+
+@chat_mcp.tool()
+def send_message(message: str) -> str:
+    """Send a chat message"""
+    return f"Message sent: {message}"
+
+
+# Default behavior: endpoints will be at /api/mcp and /chat/mcp
+default_app = Starlette(
+    routes=[
+        Mount("/api", app=api_mcp.streamable_http_app()),
+        Mount("/chat", app=chat_mcp.streamable_http_app()),
+    ]
+)
+
+# To mount at the root of each path (e.g., /api instead of /api/mcp):
+# Configure streamable_http_path before mounting
+api_mcp.settings.streamable_http_path = "/"
+chat_mcp.settings.streamable_http_path = "/"
+
+configured_app = Starlette(
+    routes=[
+        Mount("/api", app=api_mcp.streamable_http_app()),
+        Mount("/chat", app=chat_mcp.streamable_http_app()),
+    ]
+)
+
+# Or configure during initialization
+mcp_at_root = FastMCP("My Server", streamable_http_path="/")

examples/snippets/servers/streamable_starlette_mount.py

@@ -47,3 +47,8 @@ async def lifespan(app: Starlette):
     ],
     lifespan=lifespan,
 )
+
+# Note: Clients connect to http://localhost:8000/echo/mcp and http://localhost:8000/math/mcp
+# To mount at the root of each path (e.g., /echo instead of /echo/mcp):
+# echo_mcp.settings.streamable_http_path = "/"
+# math_mcp.settings.streamable_http_path = "/"