curl --request GET \
  --url https://api.mn.co/admin/v1/networks/{network_id}/custom_fields \
  --header 'Authorization: Bearer <token>'

{
  "items": [
    {
      "id": "1234",
      "created_at": "2025-12-29T18:18:06+00:00",
      "updated_at": "2025-12-29T18:18:06+00:00",
      "title": "Favorite Color",
      "response_type": "dropdown_single_select"
    }
  ],
  "links": {
    "self": "<string>",
    "next": "<string>"
  }
}