How to get total number of leads using API ?

How to get total number of leads using API ?

I am using Zoho CRM API and have gone through getRecords method as mentioned on https://www.zoho.com/crm/help/api/getrecords.html

But there is no any way to get total number of leads ?
Also, should we can get list of leads with specific field value search For ex : I want leads having last name as "Thomas" ?

Please let me know.