Structured Outputs

Getting consistent, machine-parseable responses from AI models instead of free-form text. This is an introduction to the subject — for the full depth on JSON mode, schema definition, and error handling, see the JSON Mode guide.

Why Structured Outputs Matter

Free-form text is natural for human consumption but unreliable for automation. Structured outputs solve:

Problem	Free-Form Text	Structured Output
Parsing	Regex, NLP, or manual extraction needed	Direct JSON parsing
Consistency	Format varies between generations	Schema-enforced structure
Validation	Ad-hoc checks for completeness	Schema validation at the field level
Automation	Requires human review at each step	Direct integration into pipelines
Typing	All values are strings	Native data types (number, boolean, array)

Approaches to Structured Outputs

Approach	Mechanism	Reliability
JSON Mode	Model instructed to output valid JSON	Good — relies on prompting
Schema-Constrained	Model constrained to a grammar/schema	Very High — enforced at generation level
Tool/Function Calling	Output formatted as a function call	High — built into model training
Post-Processing	Parse and validate after generation	Variable — depends on parser
Two-Step	Generate text, then extract structure	Moderate — two chances for error

Schema Design Principles

Be Specific: Define exact field names, types, and constraints. A precise schema produces more reliable outputs than a loose one.

Keep It Flat: Deeply nested schemas increase error rates. Flatten where possible.

Use Optional Fields: Mark fields as optional when the data may not be available, rather than relying on null sentinels.

Provide Examples: Include a sample valid output in the prompt to show the exact format expected.

Note:

Validate everything. Always validate structured outputs against your schema before using them. Even with JSON mode or constrained generation, models can produce unexpected values.

Topics in This Section

JSON Mode - Using JSON mode for reliable, parseable AI outputs with schema definition, validation, and error handling patterns

Structured Outputs