Hermes is the messenger god, but according to Prometheus he's nothing but a glorified servant. He only shows up at the end, but that's long enough for Prometheus to call him "more senseless than a child" (987)—and to totally laugh at Hermes's attempts to scare him into revealing what he knows about Zeus's eventual destroyer. Check out what Hermes says:
In the first place, the Father will tear this rugged ravine wall into fragments with his thunder and the fire of his lightning-bolt, and will bury you under it, gripped in the embrace of the rocks. After the completion of a vast length of time, you will come back again to the light; and then, I tell you, the winged hound of Zeus, the bloodthirsty eagle, will greedily butcher your body into great ragged shreds, coming uninvited for a banquet that lasts all day, and will feast on your liver, which will turn black with gnawing. (1014-42)
Okay, we're quaking in our boots—but Prometheus basically just laughs. The impression we get here is that Hermes, like Hephaestus, is just another servant to Zeus: weak, ineffectual, and all but enslaved.