curl --request GET \
  --url https://api.hubapi.com/crm/associations/2026-03/{fromObjectType}/{toObjectType}/labels \
  --header 'Authorization: Bearer <token>'

{
  "results": [
    {
      "category": "HUBSPOT_DEFINED",
      "typeId": 123,
      "label": "<string>"
    }
  ]
}