CCR Stats - Using Watcher

We have CCR enabled in Elasticsearc and there are few indices getting replicated. Is there a way to setup monitoring alert using watcher script by querying _ccr/stats and trigger an alert if data is not getting replicated ?

I think this is possible, but we don't have this kind of watcher (in particular) out of the box. Should be pretty straight forward to implement by querying _ccr/stats and matching replicas. Here is a helpful guide to get started: https://www.elastic.co/guide/en/elasticsearch/reference/current/how-watcher-works.html

I'm trying to write a query to extract "time_since_last_read_millis" from _ccr/stats using GET.
Is there a way to extract only fields from _ccr/stats instead of getting field from hostname:port/_ccr/stats