Close. The body for AddInterfacesOnNode should look like this:
[ 256, [
{
"ifIndex": 83886080,
"Caption": "mgmt0 · MGMT:descriptionText",
"ifType": 6,
"ifSubType": 0,
"InterfaceID": 0,
"Manageable": true,
"ifSpeed": 0
},{
"ifIndex": 335544419,
"Caption": "loopback99 · Failover mechanism",
"ifType": 24,
"ifSubType": 0,
"InterfaceID": 0,
"Manageable": true,
"ifSpeed": 0
},{
"ifIndex": 369098752,
"Caption": "port-channel1 · descriptionText",
"ifType": 53,
"ifSubType": 0,
"InterfaceID": 0,
"Manageable": true,
"ifSpeed": 0
}
],
"AddDefaultPollers"
]
All I did was change the outer delimiter from { } to [ ] since you always send a json array to any Invoke call.
There are two options for the third parameter: "AddDefaultPollers" and "AddNoPollers". If you send "AddNoPollers" then no statistics will be collected - you would have to know which pollers to add and add them using a bunch of Create calls for Orion.Pollers. I would recommend sticking with AddDefaultPollers. If there is something you don't want collected (maybe you don't care about interface errors for some reason), you could always just pass AddDefaultPollers and then Delete any Orion.Pollers entries you don't want.