Couldn't get the API for returns (RMA)

As the returns are processed in Magento 2 using the Third Party - Amasty, therefore we need to know that - can the returns (RMA) be fetched through the standard API, or do we need to make any configuration setting in the Magento 2 to get the returns through the API.

API is not working - https://hspdiesel.com/rest/default/V1/returns

[edited by moderator]