---
title: Structured Output — AI Glossary
description: Structured output constrains a model to return data in a specified machine-readable format, such as JSON matching a schema, rather than free-form prose. This makes responses reliably parseable by downstream code and is essential for function calling, data extraction, and integrating models into software pipelines.
canonical: https://prompeteer.ai/glossary/structured-output
---

# Structured Output

Structured output constrains a model to return data in a specified machine-readable format, such as JSON matching a schema, rather than free-form prose. This makes responses reliably parseable by downstream code and is essential for function calling, data extraction, and integrating models into software pipelines.

## Definition

Applications often need a model's answer as data, not paragraphs. Structured output enforces a target shape — commonly JSON conforming to a provided schema — so the response can be validated and consumed programmatically without brittle text parsing. Providers offer modes that guarantee syntactically valid, schema-conformant output.

Structured output underpins function calling and tool use, where arguments must match a declared schema, and it powers reliable extraction and classification tasks. It shifts effort from cleaning up model text to defining the schema, and pairs naturally with validation as a guardrail.

## Sources

- [OpenAI — Structured Outputs guide](https://platform.openai.com/docs/guides/structured-outputs)
- [Anthropic — Increase output consistency (control output format)](https://docs.anthropic.com/en/docs/test-and-evaluate/strengthen-guardrails/increase-consistency)

## Related terms

- [function-calling](https://prompeteer.ai/glossary/function-calling)
- [tool-use](https://prompeteer.ai/glossary/tool-use)
- [guardrails](https://prompeteer.ai/glossary/guardrails)
- [evaluation](https://prompeteer.ai/glossary/evaluation)