Ever want to get into the nuts and bolts of AGOL or Portal and see the JSON behind the scenes? Well check out ago-assistant.
This application was developed by a follow co-worker, and it's awesome! It's a nice GUI based application that gives you fine grained access to your site's information.
I find this tool coupled with fiddler can help you easily debug your applications, or better help you understand the ArcGIS REST API that performs the magic.
You can grab it from github here: https://github.com/Esri/ago-assistant
Enjoy and check it out.