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Install FastMCP

We recommend using uv to install and manage FastMCP.
Or with pip:
FastMCP 4 is in prerelease. The commands above install the latest stable release, which is still 3.x. To get v4, pin the beta explicitly with pip install "fastmcp==4.0.0b1", or see Install the v4 Prerelease for the uv constraint you’ll need.

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Optional Dependencies

FastMCP provides optional extras for specific features. For example, to install the background tasks extra:
See Background Tasks for details on the task system.

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Verify Installation

To verify that FastMCP is installed correctly, you can run the following command:
You should see output like the following:

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Dependency Licensing

FastMCP depends on Cyclopts for CLI functionality. Cyclopts v4 includes docutils as a transitive dependency, which has complex licensing that may trigger compliance reviews in some organizations.If this is a concern, you can install Cyclopts v5 alpha which removes this dependency:
Alternatively, wait for the stable v5 release. See this issue for details.

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Upgrading

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From FastMCP 3.0

Most FastMCP 3 servers run on 4 without changes. See Upgrading from FastMCP 3 for the breaks that do exist, and What’s New for what the new version adds.

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From FastMCP 2.0

See the Upgrade Guide for a complete list of breaking changes and migration steps.

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From the MCP SDK

Which guide you want depends on which mcp version you’re on and which of its two server APIs you used.

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From the high-level server

If you’re using FastMCP 1.0 via SDK v1 (meaning you import FastMCP as from mcp.server.fastmcp import FastMCP), upgrading is straightforward — for most servers it’s a single import change. See Upgrading from MCP SDK v1, which also explains why that route is usually easier than moving to MCP SDK v2. If you already moved to SDK v2 and write against MCPServer, see Upgrading from MCP SDK v2 — that migration is mostly renaming.

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From the low-level server

If you built your server directly on the mcp package’s Server class, the guide you want depends on how its handlers are registered. Decorators like @server.list_tools() mean SDK v1 — see Upgrading from the Low-Level SDK v1. Handlers passed to the constructor as on_list_tools= mean SDK v2 — see Upgrading from the Low-Level SDK v2.

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Troubleshooting

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import fastmcp fails after a pip upgrade

This affects one specific case: upgrading to FastMCP 3.3 or later from FastMCP 3.2 or earlier with pip. Fresh installs and uv upgrades are unaffected, so you can skip this unless you did exactly that. If import fastmcp raises ModuleNotFoundError, or from fastmcp import FastMCP raises ImportError, immediately after the upgrade, your install is in a half-removed state. Reinstall in a single step:
If that doesn’t resolve it, remove both distributions and reinstall from a clean state:
FastMCP 3.3 moved the importable code from the fastmcp distribution into fastmcp-slim. During a single-command pip upgrade, pip can install the new files and then delete them while uninstalling the old fastmcp distribution, whose file manifest still lists those paths. uv uninstalls before it installs, so it is unaffected.

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Versioning Policy

FastMCP follows semantic versioning with pragmatic adaptations for the rapidly evolving MCP ecosystem. Breaking changes may occur in minor versions (e.g., 2.3.x to 2.4.0) when necessary to stay current with the MCP Protocol. For production use, always pin to exact versions:
See the full versioning and release policy for details on our public API, deprecation practices, and breaking change philosophy.

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Contributing to FastMCP

The Contributing Guide covers setting up a development environment, running the test suite and pre-commit hooks, and the standards we hold contributed code to.