Could GET /invoices list result contain exchange_rate field?

Could GET /invoices list result contain exchange_rate field?

Hi,

I am implementing Integration to zoho books using API v3. I would like to generate charts for net incomes and expenses etc. using data coming from zoho. Since invoices can be of different currencies, I would really love if list result would contain not only currency type but exchange rate as well. One can get the exchange rate if I do a request for a specific invoice, but this would mean extra requests, which is not good for you (extra load on servers) and for us, extra waiting time. Is there any way to tell with a param what kind of fields I would like to retrieve similarly to how FB api works. Or alternative is it very hard to add the exchange rate to the result list items?

Erich