```
{
  "type": "object",
  "properties": {
    "milestones": {
      "type": "array",
      "items": {
        "$ref": "#/$defs/milestone"
      }
    },
    "project_status": {
      "type": "string",
      "enum": ["planning", "in_progress", "completed", "on_hold"]
    }
  },
  "$defs": {
    "milestone": {
      "type": "object",
      "properties": {
        "title": {
          "type": "string",
          "description": "Milestone name"
        },
        "deadline": {
          "type": "string",
          "description": "Due date in ISO format"
        },
        "completed": {
          "type": "boolean"
        }
      },
      "required": ["title", "deadline", "completed"],
      "additionalProperties": false
    }
  },
  "required": ["milestones", "project_status"],
  "additionalProperties": false
}
```

---

## Structured Outputs: Json Object Mode (js)