CURSOR RULESPython FastAPI Cursor Rules (.mdc) | Free & Offline
Production-grade architectural rulebook for Python FastAPI & Pydantic v2. Engineered to eliminate LLM hallucinations, enforce strict deterministic conventions, and prevent architectural drift across Cursor IDE, Claude Code CLI, and autonomous multi-agent pipelines.
.cursor/rules/fastapi.mdcFailure Patterns Prevented for Python FastAPI & Pydantic v2
FastAPI with Pydantic v2 requires `model_validator` instead of `@root_validator`, Field annotations, and strict async I/O. Without rules, AI models blend outdated Pydantic v1 syntax and synchronous database calls inside async handlers.
- Invokes deprecated or removed APIs from older model training weights
- Generates conflicting configuration files and invalid imports
- Silently drops type-safety, boundaries, or transaction isolation
Code Standards: Anti-Pattern vs Verified Implementation
@app.post("/users")
def make_user(data: dict):
# Missing types, sync blocking query
return db.query(data["email"])from fastapi import APIRouter, Depends, HTTPException
from pydantic import BaseModel, Field
router = APIRouter()
class UserPayload(BaseModel):
email: str = Field(..., min_length=5)
@router.post("/users")
async def create_user(payload: UserPayload, db = Depends(get_db)):
return await db.users.create(payload.model_dump())Where to Save This Rule in Your Repository
Export the rules from the interactive editor above or download the full ZIP bundle. Ensure the file is placed at the exact path below relative to your project root so the AI engine automatically loads it:
Cursor Rules (.mdc) Directory & Generator
Inspect the complete specification manual, glob patterns, directory rules, and all available presets in our central directory.
Technical FAQ: Python FastAPI & Pydantic v2 AI Rulebooks
Does this enforce Pydantic v2 syntax?
Yes, it specifically enforces `model_dump()`, `@field_validator`, and Pydantic v2 idioms.