rest api invoke createcontainer question

I'm trying to use the rest api invoke createcontainer verb.  In order to get the parameters right, I've had to deal with muiltiple 'cannot unpackage 6', but I'm now getting a message I don't know how to intrepret.

I'm using perl, but the json interface is simple enough that it should make no difference.

The Uri I'm POST to is: https://localhost:17778/SolarWinds/InformationService/v3/Json/Invoke/Orion.Container/CreateContainer

The JSON data I'm sending is: OUT: ["Test Group","Core","60","0","Test","true",[{"name":"Sstore-DQ","definition":"swis://./Orion/Orion.Nodes/NodeID=1"}]]

I'm getting this back from the query 'Cannot serialize parameter of type 'System.Int32' (for operation 'Invoke', contract 'IRestInformationService') because it is not the exact type 'System.Object' in the method signature and is not in the known types collection. In order to serialize the parameter, add the type to the known types collection for the operation using ServiceKnownTypeAttribute."'

Any clues?