Using api to get a size of contacts

Is there a way of using api to get a size of contacts that belong to a certain tag
the most optimized way
because we need to call this api daily
and hoping not to crash anything

get a size of contacts means total number of contacts?

if yes you can check this REST API docs:
https://developer.infusionsoft.com/docs/rest/#!/Tags/listContactsForTagIdUsingGET