curl --request GET \
  --url https://api.itellico.ai/v1/accounts/{account_id}/subaccounts \
  --header 'X-API-Key: <api-key>'

{
  "count": 123,
  "items": [
    {
      "id": "<string>",
      "name": "<string>",
      "is_active": true,
      "created": "<string>",
      "modified": "<string>",
      "parent_account_id": "<string>"
    }
  ]
}