| x-vol-catalog | request and response | The identifier of the catalog. Your first catalog is 1, the second catalog is 2, and so on. |
| x-vol-master-catalog | request and response | The identifier of the master catalog. Your first master catalog is 1, the second catalog is 2, and so on. |
| x-vol-site | request and response | The unique identifier of the site. This number can be found in the URL of the live site as well as some areas of the Admin, such as under System > Structure > Site, preceded by an “s-”. For example: https://t0000.sandbox.mozu.com/Admin/s-**11111**/website in a sandbox environment. |
| x-vol-tenant | request and response | The unique identifier of the tenant. This number appears in your site’s URL in Admin, preceded by a “t”. For example: https://t**0000**.sandbox.mozu.com/Admin/m-1/ in a sandbox environment. |
| x-vol-has-error | response | If true (1), the response contains an error. |
| x-vol-locale | request and response | The code of the content locale. For example: en-US |
| x-vol-version | request and response | The version of the API to use in the request. If the version is not specified, the request uses the latest available version. |
| x-vol-currency | request and response | The three-letter ISO 4217 standard global currency code. For example: USD |
| x-vol-purchase-location | request | The location code of the store that you want to restrict your call to, such as for querying products only at that particular location. |
| x-vol-pricelist | request | The code of the pricelist that you want to restrict your call to, such as when querying for products. |
| x-vol-correlation | request | An optional GUID used to associate multiple log entries in a cascading chain of API requests. |
| x-vol-dataview-mode | request | The mode in which to view runtime data, which is Live or Pending. |
| x-api-version | request | Used only with the Products API to indicate whether Version 1 or 2 is being used (value “1” or “2”). Version 2 allows support for multi-locale catalogs and is the default for all new implementations as of May 2024. |