Structured Output — AI Glossary

Reference details

Related terms

• JSON Mode (Structured Output)
• Function Calling
• Output Parser

Example: Asked for JSON vs. constrained to JSON

Ask politely for JSON and you will eventually get a fenced code block, a trailing comma, or a helpful sentence before the object — rare enough to pass review, frequent enough to page someone. Constrained decoding makes invalid tokens unreachable during generation, so the output is valid by construction rather than by luck, and your parser stops being a source of incidents.

Commonly confused with

Schema-valid is not correct. Constrained decoding guarantees shape, never truth: a response can satisfy the schema perfectly and still put the wrong value in every field. Validation checks the container, not the contents.

When to use it

Reach for it when:

• The output feeds code, a database or an API rather than a human
• You need fields present and typed so downstream logic can rely on them
• You are extracting records from unstructured text

Reach for something else when:

• The reader is a person — schemas make prose worse
• The schema is very large or deeply nested; quality degrades and latency rises
• You are treating validity as accuracy and skipping evaluation

Referenced by

This term is used by the following ModelRefs references:

• json mode
• constrained generation
• json schema tool call
• learn prompt engineering
• build document intelligence
• openai builder path

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