# Structured Output

Source: https://customlabs.io/glossary/structured-output/
Updated: 2026-09-13

Agents

# Structured Output

Structured output constrains a model's response to a defined schema instead of free-form prose.

It lets the calling code parse the result reliably, without brittle regex or string matching.

It is foundational to tool calling and agent loops, where a wrongly-shaped response breaks the next step.

Enforcing and validating the schema is what makes it dependable, more than simply asking nicely for JSON.

[Insight: Evals before you ship](https://customlabs.io/insights/evals-before-you-ship/)[Capabilities](https://customlabs.io/capabilities/)

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## Related terms

[Tool Calling Tool calling lets a model request a structured action instead of only generating text.](https://customlabs.io/glossary/tool-calling/)[Tool Contract A tool contract is the schema a tool exposes to a model.](https://customlabs.io/glossary/tool-contract/)

## More in Agents

[Agent (Agentic AI) An agent is an LLM given a loop, memory, and tools it can call.](https://customlabs.io/glossary/agent/)[Model Context Protocol (MCP) MCP is an open standard for connecting LLM applications to tools and data sources.](https://customlabs.io/glossary/model-context-protocol/)[Context Engineering Context engineering decides what occupies a model's context window at every step, and in what order.](https://customlabs.io/glossary/context-engineering/)[Idempotency An idempotent operation produces the same result no matter how many times it runs.](https://customlabs.io/glossary/idempotency/)