Describing relates various verbs to various action names. The verb to describe means the describing relation.
[The verb wear describes the wearing action.]
To attack is a verb. The verb attack describes the attacking action.
The commented out line gives the following compiler error:
Am I doing something wrong? I checked mantis and didn’t see this reported.
I bet this is the source of the conflict, although in principle the compiler should be able to keep it straight. I think that relations on verbs may not have been tested yet; verbs only became first-class objects in the last release.
Now that I test it, I see that the problem message has an addendum: “(It may help to know that I am reading the primary verb here as ‘wear’, not ‘describes’.)”