Although neither of the character's names were given, one S.H.I.E.L.D. agent is a combat and weapons expert, while the other agent specializes in munitions. Both of these roles have past ties to both Agent Coulson (Clark Gregg) and Agent Ward (Brett Dalton).
Since both of these descriptions are rather vague, it isn't known if these characters have been created specifically for the show, or if they come from the Marvel comic books. It isn't known how many episodes these agents will appear in during the last half of Season 1.
The series returns after a brief one-week break with the mid-season finale "The Bridge", airing Tuesday, December 10 at 8 PM ET on ABC. That episode features the return of Mike Peterson (J. August Richards) from the Pilot episode.