Structured Output Patterns: Getting Reliable JSON from LLMs

Calendar February 22, 2026
Agent-Tooling
Intermediate
Output-Parsing, Schema-Design
Structured-Output, Json, Schema-Validation, Function-Calling
Python, Typescript, Json-Schema

Structured Output Patterns#

Agents need structured data from LLMs – not free-form text with JSON somewhere inside it. When an agent asks a model to classify a bug as critical/medium/low and gets back a paragraph explaining the classification, the agent cannot act on it programmatically. Structured output is the bridge between LLM reasoning and deterministic code.

Three Approaches#

JSON Mode#

The simplest approach. Tell the API to return valid JSON and describe the shape you want in the prompt.