Structured Output
definition
Structured output constrains model responses to follow specific formats like JSON, XML, or schemas defined by JSON Schema, ensuring that agents produce machine-parseable output rather than free-form text. This is critical for agent systems where tool calls require precisely formatted parameters and downstream code needs to parse model output reliably — a single missing field or wrong type can crash an entire agent pipeline.
Structured output constrains model responses to follow specific formats like JSON, XML, or schemas defined by JSON Schema, ensuring that agents produce machine-parseable output rather than free-form text. This is critical for agent systems where tool calls require precisely formatted parameters and downstream code needs to parse model output reliably — a single missing field or wrong type can crash an entire agent pipeline. Most providers now support structured output natively through response format parameters or tool-use schemas, making it possible to guarantee valid output structure without fragile regex parsing or post-hoc validation. The practical impact is enormous: structured output eliminates an entire class of integration bugs and makes agents composable, since the output of one agent call can be reliably fed as input to another. This concept connects to JSON schema for defining the structural format, function calling for the tool-use interface, and error handling tools for managing cases where structured output still produces logically invalid content.