[
  {
    "type": "source_component",
    "source_component_id": "nested",
    "ftype": "part",
    "name": "IMPORTED_ASSEMBLY"
  },
  {
    "type": "cad_component",
    "cad_component_id": "nested_model",
    "source_component_id": "nested",
    "model_step_url": "https://models.example/nested.step",
    "position": { "x": 0, "y": 0, "z": 0 }
  }
]