---
schema: rendered-html/v1
title: "FAQ - FastMCP"
source_url: https://gofastmcp.com/more/faq
generated_at: 2026-06-11T19:35:39.924423+00:00
---




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- [PrefectHQ/fastmcp](https://github.com/PrefectHQ/fastmcp "PrefectHQ/fastmcp")
- [PrefectHQ/fastmcp](https://github.com/PrefectHQ/fastmcp "PrefectHQ/fastmcp")



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FAQ






















- [import fastmcp stopped working after I upgraded with pip](#import-fastmcp-stopped-working-after-i-upgraded-with-pip)
- [What’s the difference between fastmcp and fastmcp-slim?](#what%E2%80%99s-the-difference-between-fastmcp-and-fastmcp-slim)

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# FAQ


Answers to common questions about installing and using FastMCP


## [​](#import-fastmcp-stopped-working-after-i-upgraded-with-pip) `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](gofastmcp__com__getting-started__installation.md) for the clean-reinstall fallback and an explanation of why it happens.

## [​](#what’s-the-difference-between-fastmcp-and-fastmcp-slim) 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.

[Changelog

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