Downloading a CSV file with with high-level summary information for accounts, statements, 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 account IDs is 500. If you need to download more than 500 accounts, you will need to make multiple requests. The format of the generated CSV is separate from and will not exactly match the JSON you receive from the API endpoint.