As per the link https://www.mongodb.com/docs/ops-manager/current/reference/api/measures/get-host-process-system-measurements/ and below API :

curl --user "{PUBLIC-KEY}:{PRIVATE-KEY}" --digest
--header "Accept: application/json"
--include
--request GET "https://{OPSMANAGER-HOST}:{PORT}/api/public/v1.0/groups/{PROJECT-ID}/hosts/{HOST-ID}/measurements?granularity={TIME-INCREMENT}&period={PERIOD}}&pretty=true"

This will give us the details pertaining to one host and one project. However what if one host has multiple processes and part of multiple replica sets within same project in OPS Manager? Then it becomes difficult to gather gather data. Hence a clusterid parameter should also be added to distinguish details based on host pertaining to which cluster or replica set along with projectid which is already present.