curl --request GET \
  --url https://api-m.sandbox.paypal.com/v1/notifications/webhooks-lookup \
  --header 'Authorization: Bearer <token>'

{
  "webhooks_lookups": [
    {
      "id": "<string>",
      "client_id": "<string>",
      "links": [
        {
          "href": "<string>",
          "rel": "<string>",
          "method": "GET"
        }
      ]
    }
  ]
}