HelixAdmin.addInstance()

[Massimo Calderoni]

Question over HelixAdmin.addInstance(clusterName, instanceConfig), for me to 
understand the registration process: 
is it correct to say that by adding an instance, admin only needs its id? 
In other words, if the method signature were: 
addInstance(String clusterName, String id) 
would it be the same thing?