How can i get jira ticket id by REST API?

We have an integration with jira to associate tickets with issues.
Also, we are using freshservice API to get ticket information and show it in another app, but when I see response of API, there is no field that contains issue id from JIRA issue

Could you help me ?

I would be interested too, as I have the same question for the Freshdesk variant of the Jira App.
I am afraid, that the app stores the tickets in its key-value storage - Which is not accessible from outside the app.

Anyone to confirm this?