What we did is we created a UnDP (Universal device poller) that get this data from SNMP and added that poller to the node. Works fine for Memory and CPU, but not for volumes. We are still working on adding volumes to the node.
This is the post where I show how I did it.
It's using python and swis, but using this:
You should be ok to turn my python call into REST call.
Python code here:
Hope this helps.
You may want to look at the option of using the Discovery API, which will add the node "with all the toppings", and then adjust from there. See Triggering discovery of SNMPV2 device through JSON API for an example.