[4/n] Add docs for MCP

Just adding docs.
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This commit is contained in:
Rohan Mehta 2025-03-25 13:25:50 -04:00
parent 4f8cbfa676
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# Model context protocol
The [Model context protocol](https://modelcontextprotocol.io/introduction) (aka MCP) is a way to provide tools and context to the LLM. From the MCP docs:
> MCP is an open protocol that standardizes how applications provide context to LLMs. Think of MCP like a USB-C port for AI applications. Just as USB-C provides a standardized way to connect your devices to various peripherals and accessories, MCP provides a standardized way to connect AI models to different data sources and tools.
The Agents SDK has support for MCP. This enables you to use a wide range of MCP servers to provide tools to your Agents.
## MCP servers
Currently, the MCP spec defines two kinds of servers, based on the transport mechanism they use:
1. **stdio** servers run as a subprocess of your application. You can think of them as running "locally".
2. **HTTP over SSE** servers run remotely. You connect to them via a URL.
You can use the [`MCPServerStdio`][agents.mcp.server.MCPServerStdio] and [`MCPServerSse`][agents.mcp.server.MCPServerSse] classes to connect to these servers.
For example, this is how you'd use the [official MCP filesystem server](https://www.npmjs.com/package/@modelcontextprotocol/server-filesystem).
```python
async with MCPServerStdio(
params={
"command": "npx",
"args": ["-y", "@modelcontextprotocol/server-filesystem", samples_dir],
}
) as server:
tools = await server.list_tools()
```
## Using MCP servers
MCP servers can be added to Agents. The Agents SDK will call `list_tools()` on the MCP servers each time the Agent is run. This makes the LLM aware of the MCP server's tools. When the LLM calls a tool from an MCP server, the SDK calls `call_tool()` on that server.
```python
agent=Agent(
name="Assistant",
instructions="Use the tools to achieve the task",
mcp_servers=[mcp_server_1, mcp_server_2]
)
```
## Caching
Every time an Agent runs, it calls `list_tools()` on the MCP server. This can be a latency hit, especially if the server is a remote server. To automatically cache the list of tools, you can pass `cache_tools_list=True` to both [`MCPServerStdio`][agents.mcp.server.MCPServerStdio] and [`MCPServerSse`][agents.mcp.server.MCPServerSse]. You should only do this if you're certain the tool list will not change.
If you want to invalidate the cache, you can call `invalidate_tools_cache()` on the servers.
## End-to-end example
View complete working examples at [examples/mcp](https://github.com/openai/openai-agents-python/tree/main/examples/mcp).

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# `MCP Servers`
::: agents.mcp.server

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# `MCP Util`
::: agents.mcp.util

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- results.md
- streaming.md
- tools.md
- mcp.md
- handoffs.md
- tracing.md
- context.md
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- ref/models/interface.md
- ref/models/openai_chatcompletions.md
- ref/models/openai_responses.md
- ref/mcp/server.md
- ref/mcp/util.md
- Tracing:
- ref/tracing/index.md
- ref/tracing/create.md
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show_signature_annotations: true
# Makes the font sizes nicer
heading_level: 3
# Show inherited members
inherited_members: true
extra:
# Remove material generation message in footer

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import functools
import json
from typing import Any
from mcp.types import Tool as MCPTool
from .. import _debug
from ..exceptions import AgentsException, ModelBehaviorError, UserError
from ..logger import logger
from ..run_context import RunContextWrapper
from ..tool import FunctionTool, Tool
from .server import MCPServer
class MCPUtil:
"""Set of utilities for interop between MCP and Agents SDK tools."""
@classmethod
async def get_all_function_tools(cls, servers: list[MCPServer]) -> list[Tool]:
"""Get all function tools from a list of MCP servers."""
tools = []
tool_names: set[str] = set()
for server in servers:
server_tools = await cls.get_function_tools(server)
server_tool_names = {tool.name for tool in server_tools}
if len(server_tool_names & tool_names) > 0:
raise UserError(
f"Duplicate tool names found across MCP servers: "
f"{server_tool_names & tool_names}"
)
tool_names.update(server_tool_names)
tools.extend(server_tools)
return tools
@classmethod
async def get_function_tools(cls, server: MCPServer) -> list[Tool]:
"""Get all function tools from a single MCP server."""
tools = await server.list_tools()
return [cls.to_function_tool(tool, server) for tool in tools]
@classmethod
def to_function_tool(cls, tool: MCPTool, server: MCPServer) -> FunctionTool:
"""Convert an MCP tool to an Agents SDK function tool."""
invoke_func = functools.partial(cls.invoke_mcp_tool, server, tool)
return FunctionTool(
name=tool.name,
description=tool.description or "",
params_json_schema=tool.inputSchema,
on_invoke_tool=invoke_func,
strict_json_schema=False,
)
@classmethod
async def invoke_mcp_tool(
cls, server: MCPServer, tool: MCPTool, context: RunContextWrapper[Any], input_json: str
) -> str:
"""Invoke an MCP tool and return the result as a string."""
try:
json_data: dict[str, Any] = json.loads(input_json) if input_json else {}
except Exception as e:
if _debug.DONT_LOG_TOOL_DATA:
logger.debug(f"Invalid JSON input for tool {tool.name}")
else:
logger.debug(f"Invalid JSON input for tool {tool.name}: {input_json}")
raise ModelBehaviorError(
f"Invalid JSON input for tool {tool.name}: {input_json}"
) from e
if _debug.DONT_LOG_TOOL_DATA:
logger.debug(f"Invoking MCP tool {tool.name}")
else:
logger.debug(f"Invoking MCP tool {tool.name} with input {input_json}")
try:
result = await server.call_tool(tool.name, json_data)
except Exception as e:
logger.error(f"Error invoking MCP tool {tool.name}: {e}")
raise AgentsException(f"Error invoking MCP tool {tool.name}: {e}") from e
if _debug.DONT_LOG_TOOL_DATA:
logger.debug(f"MCP tool {tool.name} completed.")
else:
logger.debug(f"MCP tool {tool.name} returned {result}")
# The MCP tool result is a list of content items, whereas OpenAI tool outputs are a single
# string. We'll try to convert.
if len(result.content) == 1:
return result.content[0].model_dump_json()
elif len(result.content) > 1:
return json.dumps([item.model_dump() for item in result.content])
else:
logger.error(f"Errored MCP tool result: {result}")
return "Error running tool."

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@ -175,10 +175,10 @@ class MCPServerStdio(_MCPServerWithClientSession):
"""Create a new MCP server based on the stdio transport.
Args:
params: The params that configure the server. This includes:
- The command (e.g. `python` or `node`) that starts the server.
- The args to pass to the server command (e.g. `foo.py` or `server.js`).
- The environment variables to set for the server.
params: The params that configure the server. This includes the command to run to
start the server, the args to pass to the command, the environment variables to
set for the server, the working directory to use when spawning the process, and
the text encoding used when sending/receiving messages to the server.
cache_tools_list: Whether to cache the tools list. If `True`, the tools list will be
cached and only fetched from the server once. If `False`, the tools list will be
fetched from the server on each call to `list_tools()`. The cache can be
@ -235,11 +235,9 @@ class MCPServerSse(_MCPServerWithClientSession):
"""Create a new MCP server based on the HTTP with SSE transport.
Args:
params: The params that configure the server. This includes:
- The URL of the server.
- The headers to send to the server.
- The timeout for the HTTP request.
- The timeout for the SSE connection.
params: The params that configure the server. This includes the URL of the server,
the headers to send to the server, the timeout for the HTTP request, and the
timeout for the SSE connection.
cache_tools_list: Whether to cache the tools list. If `True`, the tools list will be
cached and only fetched from the server once. If `False`, the tools list will be