The main thing missing from “D.E.B.S.,” which is a comedy, is comedy. Apart from that, it’s a perfectly good comedy.

Based on a short film that everyone seems to agree was 10 times as funny as the feature, “D.E.B.S.” is about a top-secret government spy agency that recruits girls via a hidden test in the SAT. Without knowing what, exactly, qualified them, nubile teenage girls are brought into the D.E.B.S. organization, given a plaid-skirt schoolgirl uniform, and trained in all manner of surveillance, crime-fighting and makeup application.

The story has ultra-talented D.E.B. Amy (Sara Foster) falling in love with the sexy supervillain she and her fellow D.E.B.S. are supposed to be pursuing, Lucy Diamond (Jordana Brewster). Amy thought she was straight until she met Lucy. Now she’s the only person to fight Ms. Diamond and live to tell about it, plus she has a crush on her.

Yes, it is a fun premise, isn’t it? The production design is sharp and comic-bookish, the tone light and spoofy, and the performances energetic. Alas, it is so short on humor! Most of the jokes do connect, like in the montage where Lucy tries to become non-evil; the problem is that there aren’t enough of them. The film, written and directed by Angela Robinson, maintains a frothy sensibility that feels like it ought to be funny — or at least be TRYING to be funny — yet isn’t, and doesn’t.

Dress it up with all the kitsch in the world, this is still just a lesbian falling-in-love story, and not a very interesting one at that. The characters are two-dimensional parody characters, trapped in a movie that doesn’t know how to do parody. It’s a good idea for a short, dragged out into a feature-length film.

D+ (1 hr., 30 min.; PG-13, some profanity, some sexuality.)