Agent Skills: FastAPI Router Creator

FastAPI Router Creator

This skill guides the creation of modular, organized FastAPI routers, emphasizing maintainability and scalability.

Routing Strategies

1. Modular Router Pattern (Standard)

The most common and recommended approach for FastAPI.

Structure:

src/api/v1/endpoints/
├── users.py
├── items.py
└── auth.py

Implementation:

src/api/v1/endpoints/users.py:

from fastapi import APIRouter

router = APIRouter()

@router.get("/")
async def get_users():
    ...

src/api/v1/api.py (Aggregator):

from fastapi import APIRouter
from src.api.v1.endpoints import users, items

api_router = APIRouter()
api_router.include_router(users.router, prefix="/users", tags=["users"])
api_router.include_router(items.router, prefix="/items", tags=["items"])

2. File-Based Routing (fastapi-router)

For a Next.js-like experience where file structure dictates URLs. (Requires fastapi-router library or custom walker).

Structure:

src/app/
├── api/
│   ├── users/
│   │   ├── route.py  # Handles /api/users
│   │   └── [id]/
│   │       └── route.py # Handles /api/users/{id}

Best Practices

1. Prefixing: Use prefixes at the router include level, not inside every endpoint decorator.
2. Tags: Use tags to group endpoints in OpenAPI docs.
3. Dependencies: Apply dependencies (like auth) at the router level if they apply to all endpoints in that router.

   router = APIRouter(dependencies=[Depends(get_current_active_user)])
   

4. Version: Namespace routers by API version (v1, v2).