So, I just came across a really bad question (that's in the process of getting close votes), and the only tag was reflection, which has no description. As the relatively new person here, I don't have much of an opinion on the value of adding a description or nuking it, but I think one of the two should be done.
I think it's best to keep it. True, it cannot stand alone, but this shouldn't be an issue per se. This is adequately addressed by the new tag excerpt.
What is more important in my opinion is that it is entirely conceivable that someone favourites or ignores the tag. This usually means it has enough merit to be retained. I consider this case no different.