Control+Shift+C (Windows, Linux, Chrome OS).
Select: Network tab
and XHR
To get the the json file ( site-template ) copy and paste to a text editor / pycharm / . . .
1.) <CTRL>+<SHIFT>+E to open Mozilla Developers Networking Tools
2.) Select only “XHR” as the rest is not interesting for us.
3.) Empty Trash on left side from all the messages you already see using the UI.
4.) Cause the UI to send API messages you want to inspect (like create a Site and click the final “OK”)
5.) Check for messages on type=JSON and Method=POST (or similar) that have been created an send based on the last event.
6.) Review Response to see your intercepted JSON (check Params for API-Entry-Point)