Trying to get a project progress percentage from API

[Ankit Patel]

I looked up documentation but unable to find best way to get progress percentage by JIRA API to be integrated with KeyedIn PPM. 

We are looking to Sync 2 scenarios, At project level or parent level.

For parent level we have populated fields to track percent complete, completed issues and total issues. But not sure how we can do it at project level...