Structured output
Getting a model to return data in a strict, parseable shape — usually JSON matching a schema — instead of prose.
Structured output is when a model returns machine-readable data your code can consume directly, rather than English you have to parse. The most reliable form constrains generation to a schema at the API level, so invalid JSON is impossible rather than merely discouraged.
The schema guarantees the shape; the prompt still carries the meaning — what each field means, and what to do when a value is missing. A standing rule to use null for absent fields, rather than infer them, is what keeps a data pipeline from filling up with confident guesses.