Downloading a CSV file with statements, sites, and associated metadata is a 2 step process. The first step (this one) prepares the download and provides a URL in the response body that can be used for downloading the CSV file. The next step is to download the file using a GET request with the response body URL. The maximum number of site IDs is 500. If you need to download more than 500 sites, you will need to make multiple requests.