if you have the console access to the device, then its easier to findout the Rest call.
Just run the below command:
debug cli on
and then run the command which you want to request through Rest like below: To get Arp table
show arp all
<request cmd="op" cookie="1112336478312474" uid="500"><operations><show><arp><entry name='all'/></arp></show></operations></request>
Highligted text is your path to get the command.
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