Richard Pryor, though highly successful with his filmed concert format, has yet to find a leading role in a narrative film that exploits his comic talents. "Some Kind of Hero," now at area theaters, is the latest installment in the ongoing search for such a role. A smooth and agreeable entertainment, "Hero" is easy to enjoy while you're watching it. But ultimately it adds up to far less than you hope for at the outset.

Directed with crisp, even-tempered assurance by Michael Pressman, "Some Kind of Hero" is free of messy, disintegrating tendencies. At the same time, the movie fails to synthesize contradictory story material.

It begins as a realistic, somewhat harrowing, comedy-drama about a decent, hard-luck guy confronting a heap of frustrating problems with limited options available to him. It ends as a playful caper comedy. The eventual letdown is caused by the realization that a believable dilemma is being resolved in a trite, far-fetched way.

The hero is a modest, unheroic GI named Eddie Keller whose unlucky streak begins the first day his squad sees action in Vietnam in 1968. Caught in an ambush, the patrol is shot up and dispersed. Eddie, a radioman, ends up a captive and spends the next six years languishing in a POW camp in North Vietnam. A joyous homecoming is gradually undermined by one piece of bad news after another: Eddie's wife has taken up with another guy, and they've mismanaged his small business into bankruptcy; Eddie's mother has suffered a stroke, and the nursing home she's lodged at hasn't been paid for months; the Army has his back pay on hold, pending an inquiry into an episode from his imprisonment, when Eddie reluctantly signed a propaganda confession in exchange for medical treatment for a dying buddy.

Desperate for ready cash, Eddie contemplates a holdup after being an innocent bystander to a bank robbery. Attempting to duplicate this crime, Eddie nervously bungles the opportunity and flees in comic embarrassment. Befriended by a Beverly Hills call girl, Toni, played by Margot Kidder, Eddie resists her amazingly generous offer to stake him until the Army resolves his case. Instead, he blunders into a larcenous opportunity that pays off, leaving only a couple of mob torpedoes on the losing end.

The screenplay derives from a 1975 novel by James Kirkwood, who also worked on the adaptation. The good-hearted hooker and the successful criminal scam feel like tacked-on fabrications. The initial sardonic approach of presenting a basically grim story punctuated by funny moments is never quite as spontaneous or effective as it should be, but it's an exploratory method worth respecting. At least there's a witty recognition of how life tends to sneak up and catch you with your pants down, unprepared for humiliating ambushes and reversals of fortune.

Eddie is perhaps too much of a victim to bring out Pryor's most imaginative comic traits. It's a subdued and rather masochistic role. Eddie could use a little more innate cunning and self-confidence, a convincing suggestion that when the chips are down, he can really think and manuever his way out of a bind rather than squirm out providentially.

A live wire like Kidder ought to set off Pryor in funnier ways also. There's an abbreviated sex scene that has the right idea, but by and large worrywart Eddie and chipper Toni do not make a compatible romantic comedy team. She's also a little too providential to be believed. I suppose it happens, but the number of high-priced call girls who come to the rescue of lonely, hard-up GIs must be statistically infinitesimal. Is there really any compelling reason why the heroine of this story has to be a hooker?