Pydantic AI
A Python agent framework from the Pydantic team — type-safe agents with structured outputs, model-agnostic, and a thin API designed to feel like FastAPI for LLMs.
Pydantic AI started in late 2024 and shipped 1.0 in 2025. The pitch: bring Pydantic-style type safety to LLM agents. Agents are declared as Python classes, tools as decorated functions with type-annotated arguments, and outputs are Pydantic models the framework guarantees.
It is intentionally smaller and more Python-idiomatic than LangChain or LlamaIndex. Production teams running FastAPI services find Pydantic AI fits naturally — same idioms, same validation, same testing patterns.
In 2026, Pydantic AI is a fast-growing third option behind the OpenAI Agents SDK and LangGraph, especially in Python shops that already standardized on Pydantic for validation.
Frequently asked
Why pick Pydantic AI over LangGraph?+
Pydantic AI is smaller, more type-safe, and faster to learn. LangGraph wins for complex state machines and human-in-the-loop. Both are model-agnostic.