To get the cost report using the REST API:

1. Use POST /cost-report to generate a cost report, with the request body containing the startDate and endDate for the report as well as any optional filters. Your account must have the Owner or Viewer role to generate a cost report through this endpoint.

   The response includes a taskId that you can use to track the status of the report generation.

2. Use GET /tasks/{taskId} to check report generation status. The report is ready when the status is processing-completed and the response field contains a costReportId.

3. Use GET /cost-report/{costReportId} to download the generated cost report.