fastmcp/docs/v3/more/faq.mdx
Jeremiah Lowin c556f07a66
Archive v3 docs and publish v4 as the primary version (#4613)
* Archive v3 docs under /v3 and publish v4 as the primary version

* Label primary docs version v4.0.0 (alpha 1)

* Add What's New in v4 page; fix upgrade-guide phrasing; point banner at What's New

* Rewrite What's New around v4's new capabilities, not the sampling deprecation

* Lead What's New with the SDK v2 engine swap and the SEPs it brings

* State ships now (link Session State); tasks arrive next alpha

* Exclude docs/v3 frozen snapshots from doc-example import validation
2026-07-23 19:47:57 -04:00

25 lines
1.1 KiB
Text

---
title: FAQ
description: Answers to common questions about installing and using FastMCP
icon: circle-question
---
## `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](/getting-started/installation#troubleshooting) for the clean-reinstall fallback and an explanation of why it happens.
## 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:
```bash
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:
```bash
pip install "fastmcp-slim[client]"
```
Both distributions expose the same `import fastmcp`, so application code is identical regardless of which one you install.