fastmcp

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# FastMCP 🚀

<strong>Move fast and make things.</strong>

*Made with 💙 by [Prefect](https://www.prefect.io/)*

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---

The [Model Context Protocol](https://modelcontextprotocol.io/) (MCP) connects LLMs to tools and data. FastMCP gives you everything you need to go from prototype to production:

```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:

<table>
<tr>
<td align="center" valign="top" width="33%">
<a href="https://gofastmcp.com/servers/server">
<img src="https://raw.githubusercontent.com/PrefectHQ/fastmcp/main/docs/assets/images/servers-card.png" alt="Servers" />
<br /><strong>Servers</strong>
</a>
<br />Expose tools, resources, and prompts to LLMs.
</td>
<td align="center" valign="top" width="33%">
<a href="https://gofastmcp.com/apps/overview">
<img src="https://raw.githubusercontent.com/PrefectHQ/fastmcp/main/docs/assets/images/apps-card.png" alt="Apps" />
<br /><strong>Apps</strong>
</a>
<br />Give your tools interactive UIs rendered directly in the conversation.
</td>
<td align="center" valign="top" width="33%">
<a href="https://gofastmcp.com/clients/client">
<img src="https://raw.githubusercontent.com/PrefectHQ/fastmcp/main/docs/assets/images/clients-card.png" alt="Clients" />
<br /><strong>Clients</strong>
</a>
<br />Connect to any MCP server — local or remote, programmatic or CLI.
</td>
</tr>
</table>

**[Servers](https://gofastmcp.com/servers/server)** wrap your Python functions into MCP-compliant tools, resources, and prompts. **[Clients](https://gofastmcp.com/clients/client)** connect to any server with full protocol support. And **[Apps](https://gofastmcp.com/apps/overview)** give your tools interactive UIs rendered directly in the conversation.

Ready to build? Start with the [installation guide](https://gofastmcp.com/getting-started/installation) or jump straight to the [quickstart](https://gofastmcp.com/getting-started/quickstart).

## Run FastMCP in production with Horizon

FastMCP is the standard way to build MCP servers. **[Prefect Horizon](https://www.prefect.io/horizon?utm_source=github&utm_medium=readme&utm_campaign=readme_horizon&utm_content=readme_body)** is the enterprise MCP gateway for running them safely.

Built by the FastMCP team, Horizon packages the best practices we've learned shipping the world's most popular MCP framework.

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 Horizon →](https://www.prefect.io/horizon?utm_source=github&utm_medium=readme&utm_campaign=readme_horizon&utm_content=readme_cta)

## Installation

We recommend installing FastMCP with [uv](https://docs.astral.sh/uv/):

```bash
uv pip install fastmcp
```

For full installation instructions, including verification and upgrading, see the [**Installation Guide**](https://gofastmcp.com/getting-started/installation).

**Upgrading?** We have guides for:
- [Upgrading from FastMCP v2](https://gofastmcp.com/getting-started/upgrading/from-fastmcp-2)
- [Upgrading from the MCP Python SDK](https://gofastmcp.com/getting-started/upgrading/from-mcp-sdk)
- [Upgrading from the low-level SDK](https://gofastmcp.com/getting-started/upgrading/from-low-level-sdk)

> [!NOTE]
> If `import fastmcp` fails right after a `pip` upgrade from FastMCP 3.2 or earlier, run `pip install --force-reinstall fastmcp`. See [Troubleshooting](https://gofastmcp.com/getting-started/installation#troubleshooting) for why this happens (`uv` is unaffected).

## 📚 Documentation

FastMCP's complete documentation is available at **[gofastmcp.com](https://gofastmcp.com)**, including detailed guides, API references, and advanced patterns.

Documentation is also available in [llms.txt format](https://llmstxt.org/), which is a simple markdown standard that LLMs can consume easily:

- [`llms.txt`](https://gofastmcp.com/llms.txt) is essentially a sitemap, listing all the pages in the documentation.
- [`llms-full.txt`](https://gofastmcp.com/llms-full.txt) contains the entire documentation. Note this may exceed the context window of your LLM.

**Community:** Join our [Discord server](https://discord.gg/uu8dJCgttd) to connect with other FastMCP developers and share what you're building.

## Contributing

We welcome contributions! See the [Contributing Guide](https://gofastmcp.com/development/contributing) for setup instructions, testing requirements, and PR guidelines.