When downloading files via the GET Files/{FileId}/Content, there is no way to know the filename without first getting the details of the file via
GET Files/{FileId}/

This means 2 calls must be made when downloading files.

As a suggestion, to reduce pressure on the servers, the Xero API should include the content-disposition and content-type headers on GET Files/{FileId}/Content

This would be similar how we need to include those fields on POST.

This means we could simply parse these headers to find out the file name, reducing pressure on the xero api servers.