FastAPI skill

Install

uvx library-skills

This is third-party code. Review the repository files before installing.

What it does

The skill lives inside the fastapi package, so its guidance matches the framework version in the project and updates with it. It gives the agent current patterns: parameters and dependencies via Annotated, response models via return types, APIRouter-level settings, JSON Lines and Server-Sent Events streaming, and serving a built frontend with app.frontend(). It also has the agent run the server with fastapi dev and fastapi run, declare the entrypoint in pyproject.toml, and use related tools: uv, Ruff, ty, SQLModel, HTTPX. Details sit in separate reference files the agent reads when needed.

Who it is for. For Python developers building APIs with FastAPI alongside a coding agent.

Example request

Add an endpoint that streams task progress via Server-Sent Events

Limitations

The skill installs from the package already present in the project, so FastAPI must be installed first, and the install command needs uv. The skill contains coding guidance only and does not check the project automatically.

How to disable. Delete the fastapi folder from the agent's skills directory, for example .claude/skills/fastapi.

Security check

• The skill consists only of instructions and references

README in short

The repository is the FastAPI framework itself; the skill is described in the tutorial docs: it ships in the package and installs with uvx library-skills once FastAPI is in the project. SKILL.md holds a quick reference and links to references on dependencies, responses, streaming, Pydantic, routing and tooling. Release notes show the skill updated regularly alongside new framework features. MIT licensed.

SKILL.md

---
name: fastapi
description: FastAPI best practices and conventions. Use when working with FastAPI APIs, Pydantic models, dependencies, streaming responses including Server-Sent Events (SSE), and serving frontend apps. Keeps FastAPI code clean and up to date with the latest features and patterns.
---

# FastAPI

Official FastAPI skill to write code with best practices, keeping up to date with new versions and features.

## Quick Reference

* Serve frontend apps: use `app.frontend()` or `router.frontend()` for built frontend assets; see [Serve Frontend Apps](#serve-frontend-apps).
* Server-Sent Events (SSE): use `response_class=EventSourceResponse` and `yield`; see [Streaming](#streaming-json-lines-sse-bytes) and [the streaming reference](references/streaming.md).
* JSON Lines and byte streaming: see [the streaming reference](references/streaming.md).
* Dependencies: use `Annotated[..., Depends(...)]`; see [Dependency Injection](#dependency-injection) and [the dependency injection reference](references/dependencies.md) for `yield`, scopes, and class dependencies.
* Response models: prefer return types; use `response_model` when the public response schema differs from the internal return value; see [the response reference](references/responses.md).
* Pydantic models: do not use ellipsis or `RootModel`; see [the Pydantic reference](references/pydantic.md).
* Routing: declare router-level prefix, tags, and shared dependencies on the `APIRouter`; see [the path operation reference](references/path-operations.md).
* Tooling and related libraries: use uv, Ruff, ty, Asyncer, SQLModel, and HTTPX when applicable; see [the other tools reference](references/other-tools.md).

## Use the `fastapi` CLI

Run the development server on localhost with reload:

```bash
fastapi dev
```

Run the production server:

```bash
fastapi run
```

Related