Include the notes area of Invoices in the Invoices Endpoint. I have many clients that want to track who created invoices for sales tracking.
Nicolas Emmerich commented
The issue with the current notes approach in the Xero API, is that they need to be downloaded one Xero Invoice at a time. This will quickly blow out the number of calls.
A better approach would be to have the data included in the Invoices endpoint or possibly another endpoint that can return 100 invoices at a time.
Especially important is knowing who create the invoice and who approved it.