Rather than asking for JSON and hoping, the runtime constrains generation so only tokens valid under the schema can be produced. The output parses by construction, which removes an entire class of retry-and-repair code from every pipeline that consumes model output.

It does not make the content correct — a schema-valid answer can still be wrong, and an over-tight schema can push a model into inventing a value to fill a required field. Make fields nullable when the honest answer is that the model does not know.