Pydantic AI
A typed Python SDK for building AI agents that work with many LLM providers.
- Stars
- 21k
- Forks
- 3.1k
- Licence
- MIT
- Language
- Python
- Last update
- 4 days ago
- Type
- Library
What it is
Pydantic AI is a Python library for building AI agents, which are programs where a language model calls tools and returns results. Outputs are validated against Python types, so the results come back in a predictable shape. It lets you switch between model providers with a small string change and offers optional extras such as a terminal coding agent, evals, and durable execution through Temporal.
- Extract structured data such as sentiment scores from text into a validated Python object
- Give an agent custom tools that fetch data from your own code
- Run a coding agent in the terminal using the included Coder capability
- Add image generation or embeddings to a Python application
Great for
- Python developers building LLM-powered features that need structured, typed output
- Teams that want to swap or fall back between model providers without rewriting code
- Developers who already use Pydantic models and want a consistent validation approach
- People who want to run one agent across a web app, terminal, or background queue
Not ideal for
- Non-programmers looking for a ready-made chat app, since this is a code library
- Projects that must avoid a dependency on a large framework, since the README describes many optional capabilities
- Users of languages other than Python, since the project is Python-only
How to get it
- 1
Install with a package manager
You'll need: Python · uv (optional, used in the README examples)
Add the library with uv
uv add pydantic-ai - 2
Run it
- Install the library with uv add pydantic-ai
- Create an Agent with a model string such as openai:gpt-6.1-sol
- Add an output_type using a Pydantic model to get typed results
- Call agent.run_sync with a prompt and print result.output
- 3
Get the most out of it
- Use output_type with a Pydantic model to get validated, typed results
- Add tools with the @agent.tool decorator and RunContext for dependencies
- Use capabilities such as WebSearch or Advisor to extend an agent
- Use Pydantic Evals to grade agent outputs and tool-call trajectories
- Use the clai CLI to try an agent in the terminal before writing code
Downloads
Strengths
- Outputs are validated against types, so your editor and type checker can rely on them
- Supports many model providers through a single agent interface with fallback options
- Instrumentation uses standard OpenTelemetry, so it works with existing observability tools
Trade-offs
- The README covers many features and packages, so the scope may be large for a small project
- Some examples reference model names and features that you should verify against current provider docs
- Several advanced features, such as Temporal durability and the Gateway, are tied to additional services or packages
How it compares
| Project | Stars | Type | Level | Updated | Best for |
|---|---|---|---|---|---|
| pydantic-ai (this) | 21k | Library | intermediate | 4 days ago | Python developers building LLM-powered features that need structured, typed output |
| langchain | 149k | Framework | intermediate | 4 days ago | Python developers building LLM-powered applications |
| llama_index | 52.8k | Library | intermediate | 10 days ago | Python developers building retrieval-augmented generation (RAG) apps over private documents |
| crewAI | 60.4k | Library | intermediate | 4 days ago | Python developers prototyping multi-agent workflows |
| instructor | 14.1k | Library | beginner | 10 days ago | Python developers who need JSON-like data from an LLM for downstream code |
| deepagents | 30.9k | Library | intermediate | 4 days ago | Developers building AI agents that run multi-step tasks such as research and writing |
Stats synced from GitHub. The assessment above was drafted with AI from the project's README on 2026-10-29 and may miss recent changes — check the README before relying on a command. MIT licence: free to use, modify and distribute, including commercially, as long as you keep the copyright notice.