Structured Output as a Contract

A schema is a written description of the fields that an output must have, and validation is code that tests an output against that description. An object that passes validation comes with a short list of promises and a longer list of things that nobody has promised.

It promises that:

• Every required field exists.
• Each field has the declared type.
• Each value comes from the allowed list, if the field has one.

It does not promise that:

• The category is the correct category.
• The order number belongs to this customer.
• The summary is true.