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There is a neat plugin from Atlassian for discovery and testing of REST services that you can use for running requests on your Jira installation, you can get it here:
https://marketplace.atlassian.com/apps/1211542/atlassian-rest-api-browser?hosting=server&tab=overview
You can find our APIs by searching for ksso/api and uncheck the “show only public APIs” checkbox.
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