> ## Documentation Index
> Fetch the complete documentation index at: https://docs.deeda.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Structured Output

> Get schema-valid JSON out of any stage, on any provider.

**ELI5:** declare the shape you want per stage; the harness picks each
provider's native structured-output mechanism (Anthropic `output_format:
json_schema`, Gemini structured output, OpenAI structured responses) and
validates the result. You never write provider-specific JSON-mode flags.

## Where it lives: per-stage `output_schema`

There is deliberately **no top-level `structured_output` field**. Structure
belongs to stages — a stage that produces data declares its shape:

```yaml theme={null}
state_machine:
  start: extract
  stage_order: [extract, report]
  states:
    extract:
      output_schema:
        type: object
        properties:
          issues:
            type: array
            items:
              type: object
              properties:
                file: { type: string }
                severity: { type: string }
                summary: { type: string }
              required: [file, severity]
        required: [issues]
  on_event:
    extract_completed: report
  terminal_states: [done]
```

The `extract` stage must emit JSON matching this schema; the next stage
receives it as typed input. Supported `type` values: `object`, `array`,
`string`, `number`, `boolean`, with recursive `properties`/`items` and
`required`.

## Provider support

Implemented and probed on Anthropic (`output_format {type: json_schema}` and
strict JSON mode), Gemini (structured output), and the OpenAI Responses path.
Local models honor the shape on a best-effort basis — validate downstream if
your local model matters.

## When to use

| Task                                   | Use structured output?                           |
| -------------------------------------- | ------------------------------------------------ |
| Stage feeds another stage or a program | Yes — always declare `output_schema`             |
| Extraction, classification, triage     | Yes                                              |
| Prose deliverables (reports, reviews)  | No — let the stage write markdown to the workpad |

## See also

* [State & Sessions](/concepts/state-and-sessions) — how stage outputs flow
* [Workflow Schema](/harness/workflow-schema#state-machine) — exact shape