FastAPI Skill

FastAPI Skill

Loaded by: Backend Division agents | Version: 1.0

Project Structure

src/
  api/​v1/​routes/, schemas/, dependencies/
  core/​config.py, security.py
  models/
  services/
  utils/

Best Practices

Routes

from fastapi import APIRouter, Depends, HTTPException, status

router = APIRouter(prefix="/​users", tags=["users"])

@router.post("/", response_model=UserResponse, status_code=status.HTTP_201_CREATED)
async def create_user(user: UserCreate, db: Session = Depends(get_db)):
    return await UserService(db).create(user)

Error Handling

raise HTTPException(
    status_code=status.HTTP_404_NOT_FOUND,
    detail={"error": "user_not_found", "message": "User with this ID does not exist"}
)

Validation

• Pydantic models for all request/​response schemas
• Validate at schema level, not in routes
• Custom validators for business rules

Anti-Patterns

• Do NOT put business logic in routes
• Do NOT use raw SQL without parameterization
• Do NOT return database models directly (use schemas)
• Do NOT catch broad exceptions silently
• Do NOT hardcode configuration values

Checklist

• Routes use proper HTTP methods and status codes
• Request/​response schemas defined
• Error responses are structured
• Database sessions properly managed
• Authentication applied where needed