Hi,
Yes, you need to pass it as JSON. Provided curl example below to achieve the same. Here NodeID 1 is provided as input.
curl -k -u admin: -X POST -H "Content-Type: application/json" "https://localhost:17778/Solarwinds/InformationService/v3/json/Invoke/Orion.NPM.Interfaces/DiscoverInterfacesOnNode" --data "["1"]"