Instructor

Instructor is the most popular library for extracting structured data from large language models, with over 3 million monthly downloads, 11K GitHub stars, and 100+ contributors. Define a Pydantic model that specifies exactly what data you want, and Instructor handles the rest: schema generation, API calls, validation, and automatic retries when the output does not match. It works with OpenAI, Anthropic, Google Gemini, DeepSeek, Ollama, and 15+ other providers. Available in Python, TypeScript, Go, Ruby, Elixir, and Rust. For most projects that need reliable structured output from LLMs, Instructor is the safest default. It requires almost no learning curve and covers the 80% case where you just need the model to return validated JSON matching your schema.