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Pydantic AI

Typed Python agent framework from the Pydantic team for building AI agents with structured outputs across any model provider.

Visit ai.pydantic.dev ↗Alternatives
Works with AI agents:llms.txt
Ask your AI about this, with this page as the source:ChatGPT ↗Claude ↗Perplexity ↗

Pydantic AI is an open-source Python agent framework from the team behind the Pydantic validation library. It brings the same type-checked style to LLM code: tool arguments and agent outputs are defined as typed Python and validated, instead of parsed out of model text by hand.

You create an Agent with a model string such as anthropic:<model> or openai:<model>, instructions, tools (decorated Python functions whose signatures become the tool schema), and an output type, often a Pydantic model. Dependency injection passes typed services such as a database connection into tools and instructions, and lets tests swap them out. You run an agent with run, run_sync or streaming. It needs Python 3.10 or later, and pydantic-ai-slim installs only the provider extras you use.

Switching providers is a string change across OpenAI, Anthropic, Google, Bedrock, Vertex, Azure, OpenAI-compatible services and local servers. Instrumentation emits standard OpenTelemetry, so traces go to Pydantic Logfire or any OTLP backend. Durable execution integrates with Temporal, DBOS, Prefect and Restate so a run survives crashes, adapters stream to frontends built on the Vercel AI SDK or AG-UI, and TestModel lets unit tests run without real model calls. It runs in your own process; the optional Pydantic AI Gateway is hosted or self-hosted.

It is Python only. It deliberately leaves storage to you: saving a conversation means serializing the message history into your own database. Cross-conversation memory, guardrails and coding-agent tools sit in a separate Pydantic AI Harness package.

Where it fits

AI SDK & Agent Framework · Thin SDKPython agents whose outputs must validate against typed schemas, across any model provider.Trade-off: Python only, with fewer prebuilt integrations than the broad frameworks.

How Pydantic AI itself is built

5 tools, from its own code, website and Product Hunt page.

AstroClaude CodeLangChainLangSmithMongoDB

Who uses it

No maker's live product on record yet, and 35 open-source projects that declare it in their code.

Declared in code 35How evidence is collected →

We haven't found a maker's live product that uses Pydantic AI yet — only the open-source projects below, which declare it in their code.

blueking-paas蓝鲸智云 PaaS 平台是一个开放式的开发平台，让开发者可以方便快捷地创建、开发、部署和管理 SaaS 应用。它提供了完善的前后台开发框架、服务总线（ESB）、API Gate…AI SDK & Agent FrameworkIn its code · source ↗

Open source: a project that declares Pydantic AI as a dependency in its public code — verifiable, but not necessarily a live product.

Loved and watch-outs

Themes that recur in makers' words and Hacker News comments, each linked to what it summarises.

Most loved
  • Handles the agent and tool-calling loop for you and makes switching between model providers easy. HNHN 2HN 3HN 4
  • Lighter and less abstracted than LangChain or Google ADK, and familiar to anyone already using Pydantic. HNHN 2HN 3
  • Durable execution through DBOS or Temporal and OpenTelemetry-based observability are supported. HNHN 2HN 3
  • Capabilities and hooks make it a solid base for other libraries and custom harnesses. HNHN 2HN 3HN 4

Reliability and open issues

Most wanted on GitHubOpen on 2026-10-04 in pydantic/pydantic-ai, with activity in the last year — issues and feature requests by 👍.

Alternatives to Pydantic AI

All alternatives by situation →
LangChainThe largest set of ready-made integrations for models, tools and data sources, in Python and JavaScript.Open sourceFree tier65 makers · AI SDK & agent framework
LlamaIndexAgents that mostly retrieve and reason over your own documents.Open sourceFree tier16 makers · AI SDK & agent framework
MastraTypeScript and Next.js apps that want agents, workflows, memory and RAG without a Python service.Open sourceFree tier24 makers · AI SDK & agent framework
OpenAI Agents SDKA small agent loop with tools, handoffs, guardrails and tracing built in, from the OpenAI team.Open sourceFree tier1 makers · AI SDK & agent framework
AI SDKTypeScript agents with tool calling, multi-step loops and streaming to the UI, on any model provider.Open sourceFree tier4 makers · AI SDK & agent framework
Claude Agent SDKAgents that read and edit files, run shell commands and manage long context, built on the same harness as Claude Code.Open source
LangGraphStateful agents built as an explicit graph of steps, with checkpoints, retries, streaming and pauses for human approval, in Python or JavaScript.Open sourceFree tier1 makers · AI SDK & agent framework
CrewAIPython projects that split work across several role-based agents, like researcher, writer and reviewer.Open sourceFree tier3 makers · AI SDK & agent framework

Questions makers ask about Pydantic AI

Which model providers does it support?

You pick a provider with a <provider>:<model> string: OpenAI, Anthropic, Google, AWS Bedrock, Vertex AI, Azure and others, plus OpenAI-compatible services and local model servers. Each has a setup guide covering its options. source ↗

Do I have to use Logfire for observability?

No. Instrumentation emits standard OpenTelemetry spans for every model and tool call, and any OTLP backend works. Logfire is the easiest option, not a requirement. source ↗

How do I save a chat and continue it later?

Serialize the message history to JSON with ModelMessagesTypeAdapter and store it in your own database, for example in a jsonb column. The framework leaves the schema to you. source ↗

Can a run survive a crash or restart?

Yes, with durable execution. Integrations are co-maintained for Temporal, DBOS, Prefect, Restate and AWS Lambda, and a builder lets you connect another engine. source ↗

Can I use it behind a frontend built with the Vercel AI SDK?

Yes. VercelAIAdapter speaks the AI SDK data stream protocol that useChat expects; with FastAPI or another Starlette app, one call handles the request and streams the response. source ↗

How do I test agents without calling an LLM?

Swap in TestModel or FunctionModel with Agent.override, and set ALLOW_MODEL_REQUESTS=False so tests can't hit a real model by accident. source ↗

Which Python versions are supported?

Python 3.10 and later. The pydantic-ai-slim package lets you install only the extras for the providers you use. source ↗

Is Pydantic AI free?

Yes — it is free, open-source software.

Is Pydantic AI open source or self-hostable?

Open source, and you can self-host it. source ↗

Can AI coding agents work with Pydantic AI?

It serves an llms.txt docs index.

Who uses Pydantic AI?

No maker's live product we track yet; 35 open-source projects declare it in their code. source ↗