Serialisation and JSON Schema

Validation is the trip into a model. Serialisation is the trip back out: turning a Ticket with a datetime and a nested Customer into something a browser, a queue, or a language model can read. Pydantic gives you exact control over that trip, and the same model can also describe itself as a JSON Schema, so the shape you validate against is the shape you publish to clients and to tools.

The distinction to keep in mind is between a Python dump and a JSON dump. A Python dump keeps datetime and Decimal objects as they are, which is what you want when passing data between functions. A JSON dump turns them into strings and numbers that survive json.dumps, which is what you want at the edge.