I did a quick search on the internet and found very little information about this property. It was designed to help in the customization scenario.
By default, all the build workflow variables and arguments are serialized into the AgentScope activity. If for some reason you don’t want this to happen to your custom variables, such as in this Connect bug, you just need to add the variables to the AgentScope.DataToIgnore list.
One thing to note though, adding it through the custom editor when the build template is opened in Visual Studio doesn’t work (oops - see how much this property is used). You would need to edit the .xaml file directly:
<AgentScope DataToIgnore=”MyVariable1, MyVariable2” ... >