# Response schema

> Responses include a stable id, typed output array, usage estimates, and a request id. Spatial outputs can include reasoning_scene.v2, a renderable 3D reasoning layer used by Four Cad.

Source: https://fourechelon.com/docs/response-schema · Machine-readable: https://fourechelon.com/openapi.json · Index: https://fourechelon.com/llms.txt

## Response fields

| Field | Type | Description |
| --- | --- | --- |
| id | string | Unique response id. |
| object | string | The object type. Usually response. |
| model | string | The model that generated the response. |
| output | array | Typed spatial outputs for the requested task. When the request carried a cad_scene, understand, describe, and compare add output[].data.cad_scene: named objects with absolute bounds and parents, connectors with direction, spatial relations, title block, and callout counts; compare adds output[].data.cad_scene_diff (added, removed, moved, re-parented, rewired, dimensions changed). |
| usage | object | Input spatial tokens, output spatial tokens, projected input cost, projected output cost, and total estimated cost. |
| request_id | string | Request id for support and debugging. |

```json
{
  "id": "resp_4e1f45c7ebd1",
  "object": "response",
  "model": "rowe-1.0",
  "output": [
    {
      "type": "fit_result",
      "data": {
        "feasible": false,
        "confidence": 0.2862,
        "explanation": "Transformer multimodal model predicts fit feasibility=false.",
        "reasoning_scene": {
          "schema_version": "reasoning_scene.v2",
          "scene_id": "four-cad-analysis",
          "task_type": "fit",
          "objects": [],
          "relations": [],
          "overlays": [],
          "measurements": [],
          "reasoning_steps": [],
          "suggested_changes": [],
          "issue_regions": [],
          "fit_results": [],
          "comparison_results": [],
          "geometry_changes": [],
          "text_explanation": "The highlighted geometry shows why the fit check failed."
        }
      }
    }
  ],
  "usage": {
    "input_tokens": 42,
    "output_tokens": 29,
    "estimated_input_cost_usd": 0.000042,
    "estimated_output_cost_usd": 0.000116,
    "estimated_cost_usd": 0.000158
  },
  "request_id": "req_..."
}
```