∆ AI Decision Graph
engineering low complexity mvp

Structured Output

Structured output asks a model to return data in a predictable schema instead of free-form prose.

Decision

Use structured output when downstream code needs reliable fields, labels, choices, or extracted values.

Use when

  • Classification
  • Data extraction
  • Routing
  • UI-ready responses

Avoid when

  • Open-ended writing
  • Unclear schemas
  • Business rules without validation
  • Cases where humans read all output directly

Why structured output is often enough

Many AI product features need the model to produce fields, not prose. A schema can make extraction, classification, routing, and UI rendering easier to validate.

Structured output is usually simpler than function calling when no external action is needed. The model returns data, and the application decides what to do with it.

When to go beyond it

Use function or tool calling when the model needs to request an external operation. Use structured output when the output itself is the product input.

Common mistakes

  1. Asking for JSON without validating it.
  2. Making schemas too broad.
  3. Using tool calling for simple extraction.

Next decision

Start with structured output for classification and extraction. Add function calling only when the model must choose an external capability.