feat: support in-process fastmcp server

examples/mcp/in_process/README.md

@@ -0,0 +1,14 @@
+# MCP In-Process Example
+
+This example uses an in-process fastmcp server in [server.py](server.py).
+
+Run the example via:
+
+```
+uv run python -m examples.mcp.in_process.main
+```
+
+## Details
+
+The example uses the `FastMCPServer` class from `agents.mcp.fastmcp`. The server is invoked in-process like a function call.
+

examples/mcp/in_process/main.py

@@ -0,0 +1,52 @@
+import asyncio
+import os
+import shutil
+import subprocess
+import time
+from typing import Any
+
+from agents import Agent, Runner, gen_trace_id, trace
+from agents.mcp import MCPServer
+from agents.mcp.fastmcp import FastMCPServer
+from agents.model_settings import ModelSettings
+
+from .server import mcp
+
+
+async def run(mcp_server: MCPServer):
+    agent = Agent(
+        name="Assistant",
+        instructions="Use the tools to answer the questions.",
+        mcp_servers=[mcp_server],
+        model_settings=ModelSettings(tool_choice="required"),
+    )
+
+    # Use the `add` tool to add two numbers
+    message = "Add these numbers: 7 and 22."
+    print(f"Running: {message}")
+    result = await Runner.run(starting_agent=agent, input=message)
+    print(result.final_output)
+
+    # Run the `get_weather` tool
+    message = "What's the weather in Tokyo?"
+    print(f"\n\nRunning: {message}")
+    result = await Runner.run(starting_agent=agent, input=message)
+    print(result.final_output)
+
+    # Run the `get_secret_word` tool
+    message = "What's the secret word?"
+    print(f"\n\nRunning: {message}")
+    result = await Runner.run(starting_agent=agent, input=message)
+    print(result.final_output)
+
+
+async def main():
+    async with FastMCPServer(mcp) as server:
+        trace_id = gen_trace_id()
+        with trace(workflow_name="In-Process Example", trace_id=trace_id):
+            print(f"View trace: https://platform.openai.com/traces/trace?trace_id={trace_id}\n")
+            await run(server)
+
+
+if __name__ == "__main__":
+    asyncio.run(main())

examples/mcp/in_process/server.py

@@ -0,0 +1,29 @@
+import random
+
+import requests
+from fastmcp.server import FastMCP
+
+# Create server
+mcp = FastMCP("Echo Server")
+
+
+@mcp.tool()
+def add(a: int, b: int) -> int:
+    """Add two numbers"""
+    print(f"[debug-server] add({a}, {b})")
+    return a + b
+
+
+@mcp.tool()
+def get_secret_word() -> str:
+    print("[debug-server] get_secret_word()")
+    return random.choice(["apple", "banana", "cherry"])
+
+
+@mcp.tool()
+def get_current_weather(city: str) -> str:
+    print(f"[debug-server] get_current_weather({city})")
+
+    endpoint = "https://wttr.in"
+    response = requests.get(f"{endpoint}/{city}")
+    return response.text

pyproject.toml

@@ -3,7 +3,7 @@ name = "openai-agents"
 version = "0.0.11"
 description = "OpenAI Agents SDK"
 readme = "README.md"
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 license = "MIT"
 authors = [{ name = "OpenAI", email = "[email protected]" }]
 dependencies = [
@@ -14,12 +14,12 @@ dependencies = [
     "requests>=2.0, <3",
     "types-requests>=2.0, <3",
     "mcp>=1.6.0, <2; python_version >= '3.10'",
+    "fastmcp>=2.2.0"
 ]
 classifiers = [
     "Typing :: Typed",
     "Intended Audience :: Developers",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",

src/agents/mcp/fastmcp.py

@@ -0,0 +1,55 @@
+from pathlib import Path
+from typing import Any
+
+from fastmcp.client import Client, ClientTransport
+from fastmcp.server import FastMCP
+from pydantic import AnyUrl
+from mcp.types import CallToolResult, Tool
+
+from ..mcp import MCPServer
+
+
+class FastMCPServer(MCPServer):
+    """
+    Support fastmcp transport implementations, include in-memory fastmcp servers.
+    """
+
+    def __init__(
+        self,
+        transport: ClientTransport | FastMCP | AnyUrl | Path | str,
+        name: str | None = None,
+    ):
+        self._client = Client(transport)
+        if not name:
+            if isinstance(transport, FastMCP):
+                name = transport.name
+            else:
+                name = str(transport)
+        self._name = name
+
+    async def connect(self):
+        await self._client.__aenter__()
+
+    async def cleanup(self):
+        await self._client.__aexit__(None, None, None)
+
+    async def __aenter__(self):
+        await self.connect()
+        return self
+
+    async def __aexit__(self, exc_type, exc_value, traceback):
+        await self._client.__aexit__(exc_type, exc_value, traceback)
+
+    @property
+    def name(self) -> str:
+        return self._name
+
+    async def list_tools(self) -> list[Tool]:
+        return await self._client.list_tools()
+
+    async def call_tool(
+        self, tool_name: str, arguments: dict[str, Any] | None
+    ) -> CallToolResult:
+        return await self._client.call_tool(
+            tool_name, arguments, _return_raw_result=True
+        )