Building Type-Safe LLM Agents With Pydantic AI - Real Python

"Pydantic AI is a Python framework for building LLM agents that return validated, structured outputs using Pydantic models. Instead of parsing raw strings from LLMs, you get type-safe objects with automatic validation."

"Pydantic AI uses BaseModel classes to define structured outputs that guarantee type safety and automatic validation. The @agent.tool decorator registers Python functions that LLMs can invoke based on user queries and docstrings."

"Dependency injection with deps_type provides type-safe runtime context like database connections without using global state. Validation retries automatically rerun queries when the LLM returns invalid data, which increases reliability but also API costs."

"Google Gemini, OpenAI, and Anthropic models support structured outputs best, while other providers have varying capabilities."

Pydantic AI is a Python framework for building LLM agents that return validated, structured outputs using Pydantic models. Instead of parsing raw strings from LLMs, it produces type-safe objects with automatic validation. Structured outputs are defined with BaseModel classes that guarantee type safety and validate data automatically. The @agent.tool decorator registers Python functions that LLMs can invoke based on user queries and docstrings. Dependency injection with deps_type provides type-safe runtime context such as database connections without global state. Validation retries automatically rerun queries when the LLM returns invalid data, improving reliability while increasing API costs. Google Gemini, OpenAI, and Anthropic support structured outputs best, while other providers vary.

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