For example at the moment you can specify that you want a capability to:

• exist
• equal something (string)
• equal something (regex)

But there does not seem to be a way to say that you want a capability to not exist

e.g. if you wanted to tag an agent so that only one build would use it and that other builds would avoid that agent, then it would be useful if you could put one capability on the agent and have the other builds check that the capability does not exist