A significant amount of typing is required to issue the correct scrgadm and scswitch commands. For example, see How to Use Sun Cluster Administration Commands to Create a Highly Available Service That Uses the GDS and How to Use Sun Cluster Administration Commands to Create a Scalable Service That Uses the GDS.
Using the GDS with Agent Builder simplifies the process because it generates the scripts that issue the scrgadm and scswitch commands for you.