The API Explorer will show all the HTTP calls to see and do anything that can be done with HTTP calls on the Item. In MainUI go to Settings → Developer Tools → API Explorer and scroll down to the “items” endpoint.
The URL you show is an un-official and un-supported way to command an Item which is not guaranteed to work forever and only works when BasicUI is installed. The Webhook HTTP binding is a better long term option if the thing calling the URL cannot use a POST or PUT HTTP request or if it can, use the API mentioned above.