How are API calls calculated?

[katy_rodriguez]

Looking at the 'add to list' endpoint specifically. If I need to run through 1000 records, would that be 1000 API calls to add all the records to a static list?

[SanfordWhiteman]

You can send a max of 300 leads in a single call to Add to List. So you'd need 4 calls to send 1000 leads.