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

{
  "stats": {
    "total": 123,
    "unread": 123,
    "requiring_action": 123,
    "by_priority": {
      "critical": 123,
      "high": 123,
      "medium": 123,
      "low": 123
    },
    "by_category": {}
  }
}