Schema
Most A PI endpoints are at https://sandbox.billwerk.com/api/v1/ for the sandbox respectively https://app.billwerk.com/api/v1/ for the production system.
Please note that the OAuth endpoint and some client-facing endpoints such as file downloads are not under http://api/v1/. Data is sent and received as JSON.
Our API expects and returns timestamps in the ISO 8601 format (YYYY-MM-DDTHH:MM:SS.sssssssZ).