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FastAPI

Skills#backend

FastAPI's own conventions, kept current.

Best practices from the FastAPI project for APIs, Pydantic models, dependencies and streaming responses, so the code your agent writes uses the latest features and patterns.

Install this skill

npx skills add https://github.com/fastapi/fastapi --skill fastapi

Runs the open-source skills CLI in your own terminal. It asks which agents to add the skill to. Read what it tells your agent to do before you install it.

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  • Claude Code

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    npx skills add https://github.com/fastapi/fastapi --skill fastapi -a claude-code

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    Or ask Claude Code to do it

    Install the "fastapi" skill from https://github.com/fastapi/fastapi for Claude Code.
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  • Claude.ai

    Upload the ZIP

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    2. Go to Customize > Skills, press +, then Create skill.
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  • Codex

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    npx skills add https://github.com/fastapi/fastapi --skill fastapi -a codex

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    Install the "fastapi" skill from https://github.com/fastapi/fastapi for Codex.
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  • Cursor

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    npx skills add https://github.com/fastapi/fastapi --skill fastapi -a cursor

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    Install the "fastapi" skill from https://github.com/fastapi/fastapi for Cursor.
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  • GitHub Copilot

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    npx skills add https://github.com/fastapi/fastapi --skill fastapi -a github-copilot

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    Install the "fastapi" skill from https://github.com/fastapi/fastapi for GitHub Copilot.
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  • Antigravity

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    npx skills add https://github.com/fastapi/fastapi --skill fastapi -a antigravity

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    Install the "fastapi" skill from https://github.com/fastapi/fastapi for Antigravity.
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  • Gemini CLI

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    npx skills add https://github.com/fastapi/fastapi --skill fastapi -a gemini-cli

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    Install the "fastapi" skill from https://github.com/fastapi/fastapi for Gemini CLI.
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Installs
9.6K via skills.sh
GitHub
102.3K stars ↗
Last updated
1 Sept 2026
Licence
MIT

Security checks

Run by independent scanners and published on skills.sh. Their results, not a Viberation review.

  • Gen Agent Trust Hub Pass

    This skill provides comprehensive best practices for FastAPI development, emphasizing the use of modern Python features like Type Hints and Pydantic models. It explicitly promotes security by instructing the agent to use response models to filter and protect sensitive data. All recommended tools and commands are standard for the FastAPI ecosystem.

    1 Mar 2026

  • Socket Pass

    No alerts

    18 Mar 2026

  • Snyk Pass

    Risk: LOW · No issues

    1 Mar 2026

  • Runlayer Pass

    4 files scanned · No issues

    1 Mar 2026

  • ZeroLeaks Pass

    Score: 93/100 · 2 sections analyzed

    16 Apr 2026
What's inside (7 files)
  • references/dependencies.md3.3K chars
  • references/other-tools.md1.5K chars
  • references/path-operations.md1.6K chars
  • references/pydantic.md1.8K chars
  • references/responses.md1.9K chars
  • references/streaming.md2.6K chars
  • SKILL.md10.1K chars

SKILL.md, first part. Shown as plain text.

---
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
```

Prefer declaring the entrypoint in `pyproject.toml`:

```toml
[tool.fastapi]
entrypoint = "my_app.main:app"
```

When adding the entrypoint is not possible, or the user explicitly asks not to, pass the app file path:

```bash
fastapi dev my_app/main.py
```

## Use `Annotated`

Always prefer the `Annotated` style for parameter and dependency declarations. It keeps function signatures working in other contexts, respects the types, and allows reusability.

Use `Annotated` for parameter declarations, including `Path`, `Query`, `Header`, etc.:

```python
from typing import Annotated

from fastapi import FastAPI, Path, Query

app = FastAPI()


@app.get("/items/{item_id}")
async def read_item(
    item_id: Annotated[int, Path(ge=1, description="The item ID")],
    q: Annotated[str | None, Query(max_length=50)] = None,
):
    return {"message": "Hello World"}
```

Use `Annotated` for dependencies with `Depends()`. Unless asked not to, create a new type alias for the dependency to allow reusing it:

```python
from typing import Annotated

from fastapi import Depends, FastAPI

app = FastAPI()


def get_current_user():
    return {"username": "johndoe"}


CurrentUserDep = Annotated[dict, Depends(get_current_user)]


@app.get("/items/")
async def read_item(current_user: CurrentUserDep):
    return {"message": "Hello World"}
```

## Do not use Ellipsis for *path operations* or Pydantic models

Do not use `...` as a default value for required parameters or model fields. It's not needed and not recommended.

```python
from typing import Annotated

from fastapi import FastAPI, Query
from pydantic import BaseModel, Field

app = FastAPI()


class Item(BaseModel):
    name: str
    description: str | None = None
    price: float = Field(gt=0)


@app.post("/items/")
async def create_item(item: Item, project_id: Annotated[int, Query()]):
    return item
```

See [the Pydantic reference](references/pydantic.md) for more details.

## Return Type or Response Model

When possible, include a return type. It will be used to validate, filter, document, and serialize the response.

```python
from fastapi import FastAPI
from pydantic import

Key info

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