While the identification may be accurate (I don't know for sure, but probably it is), the assumption about the tooth on the cerci does not hold. The tooth on nymphs of many (perhaps all) species in this tribe tend to have the tooth located more toward the tip than in adults. This is a rather young nymph, so it could change a lot before becoming adult. The black coloring is distinctive, and may or may not help to verify the species identification. Again that may be characteristic of (or common in) a given species, but different in nymphs from adults.

Admittedly, the tooth on the cerci is very near to the tip in this individual.

Moved from Lesser Meadow Katydids.

I think this Odontoxiphidium. In your photo I see a tooth on the inside of the male cerci towards the tip. They look sort of antler-like. All Conocephalus have a tooth near the base or middle. It is immature, but I think it's safe to move genera with this one.

This is indeed a nymph, a male (female would already show at least a vestigial ovipositor), and a slender meadow katydid in the genus Conocephalus.