curl --request GET \
  --url https://api.hubapi.com/crm/v3/limits/associations/records/{fromObjectTypeId}/to \
  --header 'Authorization: Bearer <token>'

{
  "results": [
    {
      "hasRecordsAtLimit": true,
      "hasRecordsNearLimit": true,
      "objectTypeId": "<string>",
      "pluralLabel": "<string>",
      "singularLabel": "<string>"
    }
  ]
}