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Documentation Index

Fetch the complete documentation index at: https://gofastmcp.com/llms.txt

Use this file to discover all available pages before exploring further.

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import fastmcp stopped working after I upgraded with pip

This can happen when you upgrade to FastMCP 3.3 or later from FastMCP 3.2 or earlier with pip. The quick fix is pip install --force-reinstall fastmcp. See Troubleshooting for the clean-reinstall fallback and an explanation of why it happens.

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What’s the difference between fastmcp and fastmcp-slim?

fastmcp is the full distribution. Installing it gives you the complete framework — server, client, CLI, and the common integrations — and is the right choice for most users: 
pip install fastmcp
fastmcp-slim ships the same importable fastmcp package with a minimal set of required dependencies. You opt into the pieces you need through extras, which keeps environments lean when you only use part of the framework: 
pip install "fastmcp-slim[client]"
Both distributions expose the same import fastmcp, so application code is identical regardless of which one you install.