curl --request GET \
  --url https://{defaultHost}/v1/apps/{app_id}/user_meta_fields \
  --header 'Authorization: Bearer <token>' \
  --header 'X-Authorization: <api-key>'

{
  "id": "<string>",
  "user_meta_data_schema": [
    {
      "id": "field_123",
      "app_id": "<string>",
      "name": "first_name",
      "required": false,
      "visible_profile": true,
      "visible_registration": false,
      "position": 1,
      "as_verification_identifier": false,
      "created_at": "2023-11-07T05:31:56Z",
      "updated_at": "2023-11-07T05:31:56Z"
    }
  ]
}