Singular or Plural ?

For listing all the services we use the services-list command. Here, services is in plural. But if we have several commands related to services, we might end-up with a mixture of singular and plural :

services-list
service-register-as-serviceloader

Same thing could happen if we list all add-ons (here I'm supposing that the command addons-list exits) :

addons-list
addon-build-and-install  
addon-install  
addon-new-command  
addon-remove

Is the mixture or plural and singular ok ? Shouldn't it all be in singular :

addon-list
service-list