Support for http request injection propagation to tools (#816)

tests/server/fastmcp/test_integration.py

@@ -5,14 +5,18 @@ These tests validate the proper functioning of FastMCP in various configurations
 including with and without authentication.
 """
 
+import json
 import multiprocessing
 import socket
 import time
 from collections.abc import Generator
+from typing import Any
 
 import pytest
 import uvicorn
 from pydantic import AnyUrl
+from starlette.applications import Starlette
+from starlette.requests import Request
 
 import mcp.types as types
 from mcp.client.session import ClientSession
@@ -20,6 +24,7 @@ from mcp.client.sse import sse_client
 from mcp.client.streamable_http import streamablehttp_client
 from mcp.server.fastmcp import FastMCP
 from mcp.server.fastmcp.resources import FunctionResource
+from mcp.server.fastmcp.server import Context
 from mcp.shared.context import RequestContext
 from mcp.types import (
     CreateMessageRequestParams,
@@ -78,8 +83,6 @@ def stateless_http_server_url(stateless_http_server_port: int) -> str:
 # Create a function to make the FastMCP server app
 def make_fastmcp_app():
     """Create a FastMCP server without auth settings."""
-    from starlette.applications import Starlette
-
     mcp = FastMCP(name="NoAuthServer")
 
     # Add a simple tool
@@ -88,7 +91,7 @@ def make_fastmcp_app():
         return f"Echo: {message}"
 
     # Create the SSE app
-    app: Starlette = mcp.sse_app()
+    app = mcp.sse_app()
 
     return mcp, app
 
@@ -198,17 +201,14 @@ def make_everything_fastmcp() -> FastMCP:
 
 def make_everything_fastmcp_app():
     """Create a comprehensive FastMCP server with SSE transport."""
-    from starlette.applications import Starlette
-
     mcp = make_everything_fastmcp()
     # Create the SSE app
-    app: Starlette = mcp.sse_app()
+    app = mcp.sse_app()
     return mcp, app
 
 
 def make_fastmcp_streamable_http_app():
     """Create a FastMCP server with StreamableHTTP transport."""
-    from starlette.applications import Starlette
 
     mcp = FastMCP(name="NoAuthServer")
 
@@ -225,8 +225,6 @@ def make_fastmcp_streamable_http_app():
 
 def make_everything_fastmcp_streamable_http_app():
     """Create a comprehensive FastMCP server with StreamableHTTP transport."""
-    from starlette.applications import Starlette
-
     # Create a new instance with different name for HTTP transport
     mcp = make_everything_fastmcp()
     # We can't change the name after creation, so we'll use the same name
@@ -237,7 +235,6 @@ def make_everything_fastmcp_streamable_http_app():
 
 def make_fastmcp_stateless_http_app():
     """Create a FastMCP server with stateless StreamableHTTP transport."""
-    from starlette.applications import Starlette
 
     mcp = FastMCP(name="StatelessServer", stateless_http=True)
 
@@ -435,6 +432,174 @@ async def test_fastmcp_without_auth(server: None, server_url: str) -> None:
             assert tool_result.content[0].text == "Echo: hello"
 
 
+def make_fastmcp_with_context_app():
+    """Create a FastMCP server that can access request context."""
+
+    mcp = FastMCP(name="ContextServer")
+
+    # Tool that echoes request headers
+    @mcp.tool(description="Echo request headers from context")
+    def echo_headers(ctx: Context[Any, Any, Request]) -> str:
+        """Returns the request headers as JSON."""
+        headers_info = {}
+        if ctx.request_context.request:
+            # Now the type system knows request is a Starlette Request object
+            headers_info = dict(ctx.request_context.request.headers)
+        return json.dumps(headers_info)
+
+    # Tool that returns full request context
+    @mcp.tool(description="Echo request context with custom data")
+    def echo_context(custom_request_id: str, ctx: Context[Any, Any, Request]) -> str:
+        """Returns request context including headers and custom data."""
+        context_data = {
+            "custom_request_id": custom_request_id,
+            "headers": {},
+            "method": None,
+            "path": None,
+        }
+        if ctx.request_context.request:
+            request = ctx.request_context.request
+            context_data["headers"] = dict(request.headers)
+            context_data["method"] = request.method
+            context_data["path"] = request.url.path
+        return json.dumps(context_data)
+
+    # Create the SSE app
+    app = mcp.sse_app()
+    return mcp, app
+
+
+def run_context_server(server_port: int) -> None:
+    """Run the context-aware FastMCP server."""
+    _, app = make_fastmcp_with_context_app()
+    server = uvicorn.Server(
+        config=uvicorn.Config(
+            app=app, host="127.0.0.1", port=server_port, log_level="error"
+        )
+    )
+    print(f"Starting context server on port {server_port}")
+    server.run()
+
+
+@pytest.fixture()
+def context_aware_server(server_port: int) -> Generator[None, None, None]:
+    """Start the context-aware server in a separate process."""
+    proc = multiprocessing.Process(
+        target=run_context_server, args=(server_port,), daemon=True
+    )
+    print("Starting context-aware server process")
+    proc.start()
+
+    # Wait for server to be running
+    max_attempts = 20
+    attempt = 0
+    print("Waiting for context-aware server to start")
+    while attempt < max_attempts:
+        try:
+            with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+                s.connect(("127.0.0.1", server_port))
+                break
+        except ConnectionRefusedError:
+            time.sleep(0.1)
+            attempt += 1
+    else:
+        raise RuntimeError(
+            f"Context server failed to start after {max_attempts} attempts"
+        )
+
+    yield
+
+    print("Killing context-aware server")
+    proc.kill()
+    proc.join(timeout=2)
+    if proc.is_alive():
+        print("Context server process failed to terminate")
+
+
+@pytest.mark.anyio
+async def test_fast_mcp_with_request_context(
+    context_aware_server: None, server_url: str
+) -> None:
+    """Test that FastMCP properly propagates request context to tools."""
+    # Test with custom headers
+    custom_headers = {
+        "Authorization": "Bearer fastmcp-test-token",
+        "X-Custom-Header": "fastmcp-value",
+        "X-Request-Id": "req-123",
+    }
+
+    async with sse_client(server_url + "/sse", headers=custom_headers) as streams:
+        async with ClientSession(*streams) as session:
+            # Initialize the session
+            result = await session.initialize()
+            assert isinstance(result, InitializeResult)
+            assert result.serverInfo.name == "ContextServer"
+
+            # Test 1: Call tool that echoes headers
+            headers_result = await session.call_tool("echo_headers", {})
+            assert len(headers_result.content) == 1
+            assert isinstance(headers_result.content[0], TextContent)
+
+            headers_data = json.loads(headers_result.content[0].text)
+            assert headers_data.get("authorization") == "Bearer fastmcp-test-token"
+            assert headers_data.get("x-custom-header") == "fastmcp-value"
+            assert headers_data.get("x-request-id") == "req-123"
+
+            # Test 2: Call tool that returns full context
+            context_result = await session.call_tool(
+                "echo_context", {"custom_request_id": "test-123"}
+            )
+            assert len(context_result.content) == 1
+            assert isinstance(context_result.content[0], TextContent)
+
+            context_data = json.loads(context_result.content[0].text)
+            assert context_data["custom_request_id"] == "test-123"
+            assert (
+                context_data["headers"].get("authorization")
+                == "Bearer fastmcp-test-token"
+            )
+            assert context_data["method"] == "POST"  #
+
+
+@pytest.mark.anyio
+async def test_fast_mcp_request_context_isolation(
+    context_aware_server: None, server_url: str
+) -> None:
+    """Test that request contexts are isolated between different FastMCP clients."""
+    contexts = []
+
+    # Create multiple clients with different headers
+    for i in range(3):
+        headers = {
+            "Authorization": f"Bearer token-{i}",
+            "X-Request-Id": f"fastmcp-req-{i}",
+            "X-Custom-Value": f"value-{i}",
+        }
+
+        async with sse_client(server_url + "/sse", headers=headers) as streams:
+            async with ClientSession(*streams) as session:
+                await session.initialize()
+
+                # Call the tool that returns context
+                tool_result = await session.call_tool(
+                    "echo_context", {"custom_request_id": f"test-req-{i}"}
+                )
+
+                # Parse and store the result
+                assert len(tool_result.content) == 1
+                assert isinstance(tool_result.content[0], TextContent)
+                context_data = json.loads(tool_result.content[0].text)
+                contexts.append(context_data)
+
+    # Verify each request had its own isolated context
+    assert len(contexts) == 3
+    for i, ctx in enumerate(contexts):
+        assert ctx["custom_request_id"] == f"test-req-{i}"
+        assert ctx["headers"].get("authorization") == f"Bearer token-{i}"
+        assert ctx["headers"].get("x-request-id") == f"fastmcp-req-{i}"
+        assert ctx["headers"].get("x-custom-value") == f"value-{i}"
+
+
 @pytest.mark.anyio
 async def test_fastmcp_streamable_http(
     streamable_http_server: None, http_server_url: str

tests/server/fastmcp/test_tool_manager.py

@@ -9,7 +9,7 @@ from mcp.server.fastmcp.exceptions import ToolError
 from mcp.server.fastmcp.tools import Tool, ToolManager
 from mcp.server.fastmcp.utilities.func_metadata import ArgModelBase, FuncMetadata
 from mcp.server.session import ServerSessionT
-from mcp.shared.context import LifespanContextT
+from mcp.shared.context import LifespanContextT, RequestT
 from mcp.types import ToolAnnotations
 
 
@@ -347,7 +347,7 @@ class TestContextHandling:
         assert tool.context_kwarg is None
 
         def tool_with_parametrized_context(
-            x: int, ctx: Context[ServerSessionT, LifespanContextT]
+            x: int, ctx: Context[ServerSessionT, LifespanContextT, RequestT]
         ) -> str:
             return str(x)
 

tests/shared/test_sse.py

@@ -1,3 +1,4 @@
+import json
 import multiprocessing
 import socket
 import time
@@ -318,3 +319,187 @@ async def test_sse_client_basic_connection_mounted_app(
             # Test ping
             ping_result = await session.send_ping()
             assert isinstance(ping_result, EmptyResult)
+
+
+# Test server with request context that returns headers in the response
+class RequestContextServer(Server[object, Request]):
+    def __init__(self):
+        super().__init__("request_context_server")
+
+        @self.call_tool()
+        async def handle_call_tool(name: str, args: dict) -> list[TextContent]:
+            headers_info = {}
+            context = self.request_context
+            if context.request:
+                headers_info = dict(context.request.headers)
+
+            if name == "echo_headers":
+                return [TextContent(type="text", text=json.dumps(headers_info))]
+            elif name == "echo_context":
+                context_data = {
+                    "request_id": args.get("request_id"),
+                    "headers": headers_info,
+                }
+                return [TextContent(type="text", text=json.dumps(context_data))]
+
+            return [TextContent(type="text", text=f"Called {name}")]
+
+        @self.list_tools()
+        async def handle_list_tools() -> list[Tool]:
+            return [
+                Tool(
+                    name="echo_headers",
+                    description="Echoes request headers",
+                    inputSchema={"type": "object", "properties": {}},
+                ),
+                Tool(
+                    name="echo_context",
+                    description="Echoes request context",
+                    inputSchema={
+                        "type": "object",
+                        "properties": {"request_id": {"type": "string"}},
+                        "required": ["request_id"],
+                    },
+                ),
+            ]
+
+
+def run_context_server(server_port: int) -> None:
+    """Run a server that captures request context"""
+    sse = SseServerTransport("/messages/")
+    context_server = RequestContextServer()
+
+    async def handle_sse(request: Request) -> Response:
+        async with sse.connect_sse(
+            request.scope, request.receive, request._send
+        ) as streams:
+            await context_server.run(
+                streams[0], streams[1], context_server.create_initialization_options()
+            )
+        return Response()
+
+    app = Starlette(
+        routes=[
+            Route("/sse", endpoint=handle_sse),
+            Mount("/messages/", app=sse.handle_post_message),
+        ]
+    )
+
+    server = uvicorn.Server(
+        config=uvicorn.Config(
+            app=app, host="127.0.0.1", port=server_port, log_level="error"
+        )
+    )
+    print(f"starting context server on {server_port}")
+    server.run()
+
+
+@pytest.fixture()
+def context_server(server_port: int) -> Generator[None, None, None]:
+    """Fixture that provides a server with request context capture"""
+    proc = multiprocessing.Process(
+        target=run_context_server, kwargs={"server_port": server_port}, daemon=True
+    )
+    print("starting context server process")
+    proc.start()
+
+    # Wait for server to be running
+    max_attempts = 20
+    attempt = 0
+    print("waiting for context server to start")
+    while attempt < max_attempts:
+        try:
+            with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+                s.connect(("127.0.0.1", server_port))
+                break
+        except ConnectionRefusedError:
+            time.sleep(0.1)
+            attempt += 1
+    else:
+        raise RuntimeError(
+            f"Context server failed to start after {max_attempts} attempts"
+        )
+
+    yield
+
+    print("killing context server")
+    proc.kill()
+    proc.join(timeout=2)
+    if proc.is_alive():
+        print("context server process failed to terminate")
+
+
+@pytest.mark.anyio
+async def test_request_context_propagation(
+    context_server: None, server_url: str
+) -> None:
+    """Test that request context is properly propagated through SSE transport."""
+    # Test with custom headers
+    custom_headers = {
+        "Authorization": "Bearer test-token",
+        "X-Custom-Header": "test-value",
+        "X-Trace-Id": "trace-123",
+    }
+
+    async with sse_client(server_url + "/sse", headers=custom_headers) as (
+        read_stream,
+        write_stream,
+    ):
+        async with ClientSession(read_stream, write_stream) as session:
+            # Initialize the session
+            result = await session.initialize()
+            assert isinstance(result, InitializeResult)
+
+            # Call the tool that echoes headers back
+            tool_result = await session.call_tool("echo_headers", {})
+
+            # Parse the JSON response
+
+            assert len(tool_result.content) == 1
+            headers_data = json.loads(
+                tool_result.content[0].text
+                if tool_result.content[0].type == "text"
+                else "{}"
+            )
+
+            # Verify headers were propagated
+            assert headers_data.get("authorization") == "Bearer test-token"
+            assert headers_data.get("x-custom-header") == "test-value"
+            assert headers_data.get("x-trace-id") == "trace-123"
+
+
+@pytest.mark.anyio
+async def test_request_context_isolation(context_server: None, server_url: str) -> None:
+    """Test that request contexts are isolated between different SSE clients."""
+    contexts = []
+
+    # Create multiple clients with different headers
+    for i in range(3):
+        headers = {"X-Request-Id": f"request-{i}", "X-Custom-Value": f"value-{i}"}
+
+        async with sse_client(server_url + "/sse", headers=headers) as (
+            read_stream,
+            write_stream,
+        ):
+            async with ClientSession(read_stream, write_stream) as session:
+                await session.initialize()
+
+                # Call the tool that echoes context
+                tool_result = await session.call_tool(
+                    "echo_context", {"request_id": f"request-{i}"}
+                )
+
+                assert len(tool_result.content) == 1
+                context_data = json.loads(
+                    tool_result.content[0].text
+                    if tool_result.content[0].type == "text"
+                    else "{}"
+                )
+                contexts.append(context_data)
+
+    # Verify each request had its own context
+    assert len(contexts) == 3
+    for i, ctx in enumerate(contexts):
+        assert ctx["request_id"] == f"request-{i}"
+        assert ctx["headers"].get("x-request-id") == f"request-{i}"
+        assert ctx["headers"].get("x-custom-value") == f"value-{i}"