CrmSvcUtil can be extended by creating .NET extensions assemblies. Extensions can be used to filter the entities that can be created in your generated class, adding option-set enumerations, manipulating the generated code, and so on.
It is best practice to filter the number of entities created, otherwise, your class will be too large.
The Extending CrmSvcUtil with filtering and Extending CrmSvcUtil to generate option-sets enum recipes, later in this chapter, cover a couple of scenarios.