Referência

POST /customers/create
{
  "data": {
    "email": "customer@example.com",        // obrigatório
    "taxId": "12345678900",                 // opcional
    "name": "João Silva",                   // opcional
    "cellphone": "+5511999999999",          // opcional
    "zipCode": "01310-100"                  // opcional
  },
  "metadata": {                             // opcional - dados extras da sua aplicação
    "customField": "value"
  }
}

{
  "data": {
    "id": "cust_abc123xyz",
    "devMode": false,
    "email": "customer@example.com",
    "taxId": "12345678900",
    "country": "BR",
    "name": "João Silva",
    "cellphone": "+5511999999999",
    "zipCode": "01310-100",
    "metadata": {
      "customField": "value"
    }
  },
  "success": true,
  "error": null
}