If there's a decent chance that users will want to use the protocol to, e.g., determine if a result is passing or not, it would get obnoxious to have to require four namespaces.
I think? Maybe this wouldn't actually be common. Have to think about it.
W.r.t. "determine if a result is passing or not", we might also want to have a new key assing?.
Changed my mind.
Putting it in either check or prop causes one of those namespaces to have to depend on the other, and currently they're independent. That tells me it's probably a bad idea.