FastMCP vs MCP Python SDK

FastMCP 🚀

Move fast and make things.

Made with 💙 by Prefect

The Model Context Protocol (MCP) connects LLMs to tools and data. FastMCP is a full MCP application framework for servers, clients, and interactive apps. A server starts with ordinary Python:

from fastmcp import FastMCP

mcp = FastMCP("Demo 🚀")

@mcp.tool
def add(a: int, b: int) -> int:
    """Add two numbers"""
    return a + b

if __name__ == "__main__":
    mcp.run()

Why FastMCP

Building an effective MCP application is harder than it looks. FastMCP handles all of it. Declare a tool with a Python function, and the schema, validation, and documentation are generated automatically. Connect to a server with a URL, and transport negotiation, authentication, and protocol lifecycle are managed for you. You focus on your logic, and the MCP part just works: with FastMCP, best practices are built in.

That's why FastMCP is the standard framework for working with MCP. FastMCP 1.0 was incorporated into the official MCP Python SDK in 2024. Today, the actively maintained standalone project is downloaded a million times a day, and some version of FastMCP powers 70% of MCP servers across all languages.

FastMCP has three pillars:

Servers Expose tools, resources, and prompts to LLMs.

Apps Give your tools interactive UIs rendered directly in the conversation.

Clients Connect to any MCP server — local or remote, programmatic or CLI.

Servers wrap your Python functions into MCP-compliant tools, resources, and prompts. Clients connect to any server with full protocol support. And Apps give your tools interactive UIs rendered directly in the conversation.

Building in TypeScript? FastMCP for TypeScript is the official counterpart, built and maintained by the same team. Same pillars, same ideas, npm install @prefecthq/fastmcp-ts.

Ready to build? Start with the installation guide or jump straight to the quickstart.

Scale MCP with FastMCP Gateway

FastMCP handles the MCP application layer. FastMCP Gateway is the enterprise MCP gateway for scaling servers and tools across teams, with centralized governance over how they are deployed, discovered, secured, and used.

FastMCP and FastMCP Gateway are built by the same team at Prefect.

Deploy FastMCP servers from GitHub with branch previews and instant rollback. Create a private registry of every MCP your company uses. Secure access with SSO and tool-level RBAC. Get audit logs, observability, and governance across your MCP stack. Remix approved tools into purpose-built endpoints for teams and agents.

Start with FastMCP. Scale with FastMCP Gateway →

Installation

We recommend adding FastMCP to your project with uv:

uv add fastmcp

For full installation instructions, including verification and upgrading, see the Installation Guide.

Upgrading? We have guides for:

• Upgrading from FastMCP 3
• Upgrading from FastMCP 2
• Upgrading from MCP SDK v1 or v2
• Upgrading from the low-level SDK v1 or v2

📚 Documentation

FastMCP's complete documentation is available at gofastmcp.com, including detailed guides, API references, and advanced patterns.

Documentation is also available in llms.txt format, which is a simple markdown standard that LLMs can consume easily:

• llms.txt is essentially a sitemap, listing all the pages in the documentation.
• llms-full.txt contains the entire documentation. Note this may exceed the context window of your LLM.

Give your coding agent llms.txt as its starting point. See Coding Agents for version-matched documentation and the optional server authoring skill.

Community: Join our Discord server to connect with other FastMCP developers and share what you're building.

Contributing

Start with CONTRIBUTING.md for accepted contributions and the issue-assignment workflow, then follow the Contributing Guide for setup and validation. Agents should read AGENTS.md.

MCP Python SDK

Documentation

The documentation lives at https://py.sdk.modelcontextprotocol.io/.

It has a Get started guide, What's new in v2, the API reference, and the migration guide.

What is MCP?

The Model Context Protocol lets you build servers that expose data and functionality to LLM applications in a secure, standardized way. Think of it like a web API, but designed for LLM interactions. With this SDK you can:

• Build MCP servers that expose tools, resources, and prompts to any MCP host
• Build MCP clients that connect to any MCP server
• Speak every standard transport: stdio, Streamable HTTP, and SSE

Requirements

Python 3.11+.

Installation

uv add "mcp[cli]"      # or: pip install "mcp[cli]"

The cli extra adds the mcp command-line tool (mcp dev, mcp run, mcp install) on top of the SDK; install plain mcp if you don't need it. For one-off commands, uv run --with "mcp[cli]" mcp ... works without a project.

A server in 15 lines

Create a server.py:

from mcp.server import MCPServer

mcp = MCPServer("Demo")

@mcp.tool()
def add(a: int, b: int) -> int:
    """Add two numbers."""
    return a + b

@mcp.resource("greeting://{name}")
def greeting(name: str) -> str:
    """Greet someone by name."""
    return f"Hello, {name}!"

Full example: docs_src/index/tutorial001.py

That's a complete MCP server: one tool, one templated resource. Open it in the MCP Inspector:

uv run mcp dev server.py

Call add with a=1, b=2 and you get 3 back.

Notice what you did not write: no JSON Schema (a: int, b: int is the schema), no request parsing, no validation code, no protocol handling. Two type-hinted Python functions and a docstring.

Get started takes it from here.

A client in 10 lines

The same package is a full MCP client. Serve server.py over HTTP:

uv run mcp run server.py --transport streamable-http

then point a Client at it:

import asyncio

from mcp import Client

async def main() -> None:
    async with Client("http://localhost:8000/mcp") as client:
        result = await client.call_tool("add", {"a": 1, "b": 2})
        print(result.structured_content)  # {'result': 3}

asyncio.run(main())

A URL means Streamable HTTP, the transport you deploy. Client can also launch a local server as a stdio subprocess or take any custom transport; Clients has the rest.

Contributing

We are passionate about supporting contributors of all levels of experience and would love to see you get involved in the project. See the contributing guide to get started.

License

This project is licensed under the MIT License. See the LICENSE file for details.