Pydantic
Data validation and settings management using Python type annotations — the cornerstone of FastAPI and the modern AI stack
Visit Pydantic →Pydantic validates data against Python type annotations at runtime, converting and rejecting bad input based on the types you’ve already declared — no separate schema definition language required. It’s the validation layer FastAPI uses for request bodies and the foundation much of the modern AI/agent tooling stack is built on for structured LLM outputs.
Pydantic AI extends the same type-safety approach specifically to building AI agents, if you’re looking for that rather than general data validation.