Structured Output Becomes the Default Contract

Teams are moving from free-text responses to schema-constrained outputs, cutting post-processing glue code dramatically.

Across agent codebases, a quiet shift is underway: prompts are increasingly written against an explicit output schema rather than hoping for parseable prose.

The pattern is consistent. Teams that adopt constrained decoding — or simply a strict OUTPUT_FORMAT block plus validation — report far less glue code dedicated to repairing malformed responses.

What changed

The practical driver is not model quality but integration cost. A free-text answer must be parsed, validated, retried, and often re-asked. A schema-shaped answer skips all four steps.

Common acceptance criteria now show up directly in the prompt:

• Required fields listed by name
• Enum values enumerated explicitly rather than described
• Numeric ranges stated instead of “a reasonable number”
• A NULL affordance, so the model can decline rather than invent

Practical implication

If your pipeline still regex-scrapes model output, the cheapest reliability win available is adding an explicit contract and rejecting non-conforming responses instead of repairing them silently.