JQL search via REST and getting names of linked epics?

Hi all,
I am requesting issue lists using the REST intrerface from my plugins and would like to get the linked epic name with the result. But the “linked epic” field contains just the issue id of the linked epic.
Since the issue page does not show the key but the related epic name, I hoped to get this by adding “expand=renderedFields” to my search request.

Unfortunatly the result of the epic link field is empty. Do I misunderstand the meaning of “renderedFields”?
Is there anyother way to get epic names with one search request?

Btw, using the JIRA Agile API the result contains the epic name, but the search is limited to AGILE boards only. Or is there a another search possibility?

Any help would be just great.