Pydantic AI

Pydantic AI is an open-source, MIT-licensed Python agent framework from the Pydantic team that validates LLM outputs against declared schemas and supports dependency injection and multiple providers. It is ideal for Python teams building reliable, type-safe production agents.

Pydantic AI is built by the team behind Pydantic, the validation library used inside the OpenAI, Anthropic, and Google SDKs. It applies that same schema-first, type-safe approach to agents: you declare the structured output you expect and Pydantic AI validates the model's responses against it, so your application code works with typed, predictable objects instead of raw strings. It supports multiple LLM providers, dependency injection to make agents testable, and integrates with Pydantic Logfire for observability. The framework reached its V1 milestone in September 2025 and shipped a stable V2 in June 2026 with a 'harness-first' redesign, introducing capabilities as a core primitive that bundle tools, hooks, instructions, and model settings into one composable unit. That maturity, plus the Pydantic team's reputation, has made it a popular choice for Python developers who prioritize reliability and clean engineering over sprawling feature surface. Because the framework itself is open source under the MIT license, it is free to use — your only costs are the LLM providers and infrastructure you connect. It is best for Python teams building production agents where type safety, testability, and predictable I/O matter, and less suited to those wanting a no-code builder or a language-agnostic SDK.