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FastAPI + Pydantic v2: Building Type-Safe LLM API Endpoints

Practical Pydantic v2 patterns for FastAPI endpoints that wrap LLMs: model_config, field_validator, discriminated unions, and structured output validation.

Sachin Sharma
Sachin SharmaCreator
Jun 29, 2026
8 min read
FastAPI + Pydantic v2: Building Type-Safe LLM API Endpoints
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Practical Pydantic v2 patterns for FastAPI endpoints that wrap LLMs: model_config, field_validator, discriminated unions, and structured output validation.

FastAPIPydanticPythonAPI DesignLLM
Sachin Sharma

Sachin Sharma

Full Stack Developer & Mobile Engineer

Building digital experiences at the intersection of design and code. Sharing weekly insights on engineering, productivity, and the future of tech.

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