curl --request GET \
  --url https://{subdomain}.mihu.ai/api/v1/whatsapp/template-settings/merge-fields \
  --header 'Authorization: Bearer <token>'

{
  "success": true,
  "message": "Merge fields retrieved successfully",
  "data": {
    "contact_fields": [
      {
        "tag": "{{contact.name}}",
        "field": "name"
      }
    ],
    "custom_fields": [
      {
        "tag": "{{custom.car_model}}",
        "key": "car_model",
        "name": "Car Model",
        "type": "text"
      }
    ]
  }
}