Request/Response Validation with Pydantic

Day 53 of 100 Days of MLOps. Replace the loose dict your API accepts with a typed Pydantic model that declares exactly what a valid request looks like — field types, ranges, allowed values. FastAPI then validates every request automatically, rejects malformed ones with precise field-level errors, and documents the schema for free. The professional way to define an API's contract. Runs 100% locally on any OS.