curl --request GET \
  --url https://api.aimtell.com/prod/site/variables/{id} \
  --header 'X-Authorization-Api-Key: <api-key>'

[
  {
    "id": 1234,
    "id_site": 12345,
    "name": "site_identifier",
    "value": "website12345",
    "created_at": "2020-08-26 17:05:15",
    "updated_at": "2020-08-26 17:05:15",
    "snippet": "{custom_variable:site_identifier}"
  },
  {
    "id": 1235,
    "id_site": 12345,
    "name": "domain",
    "value": "website12345.com",
    "created_at": "2020-11-10 20:08:21",
    "updated_at": "2020-11-10 20:08:21",
    "snippet": "{custom_variable:domain}"
  },
  {
    "id": 1236,
    "id_site": 20599,
    "name": "source",
    "value": "aimtell",
    "created_at": "2020-08-26 17:26:51",
    "updated_at": "2020-08-26 17:26:51",
    "snippet": "{custom_variable:source}"
  }
]