Nothing weakens a story more than the storyteller's effort to explain characters who should be explaining themselves. The writer's rule is: show the villain acting villainously or the wit being witty; don't hang descriptive tags around their necks and expect the reader to believe in their reality.

Something like that also should be urged on opera directors: show me what you mean, don't tell me. Much of the time during Gotz Friedrich's production of Wagner's ''Ring'' at the Kennedy Center in Washington, I found myself wishing the German director had followed that basic narrative axiom. Instead, only by reading the elaborate critical essays in the Deutsche Oper Berlin program book or published interviews with the director himself could one understand his intent. That is like being unable to enjoy ''Madame Bovary'' without first having read a Flaubert scholar's preface.

Why, for instance, does this ''Ring'' play itself out entirely inside a gloomy tunnel? Because, we read, Mr. Friedrich took his inspiration for this 1985 Berlin production from a postcard picture of the Washington subway and a macabre Henry Moore drawing, ''The Tube.'' We further learn that the drama is enacted underground in what the director calls ''the tunnel of time'' because of some earth-scorching disaster, probably nuclear. The unbriefed observer would certainly grasp that the ''Ring'' had developed a case of tunnel vision but could not be expected to guess why.

At every step of the way, then, it is necessary to rely on the director's printed explanations. Very well, a director is hired to direct. He is entitled to a personal vision. But, to pick an example almost at random, what happens to the ''Wintersturme'' in ''Die Walkure''? At this point in Wagner's version, the door to Hunding's primitive hut blows open to reveal a moonlit vernal landscape. The tenor is moved to rhapsodize about love and spring. In Mr. Friedrich's version, an iron door the size of an airline hangar slides open and we see a backdrop of black and white splotches, perhaps meant to suggest dead flowers or trees gone moldy in polluted air. In any event, nothing to rhapsodize over.

Such purposeful contradictions abound in this ''Ring.'' Mr. Friedrich does not attempt to fit his conceptual template neatly over Wagner's work. He tries instead to make a virtue of anomalies and ironic jokes, juxtaposing jarringly different theatrical styles and historical periods without apology. Hunding's house is no rude hut but an iron-plated, industrial-age redoubt, complete with a wet bar from which Sieglinde, according to the supertitles, dispenses honey mead. Honey mead? Hunding is armed with pistol and rifle, but also carries a couple of spears. Brunnhilde sports a traditional Wagnerian helmet with foot-long wings while her Valkyrie sisters wear more up-to-date costumes apparently designed by Leopold von Sacher-Masoch: jackboots, black leather and chains.

What to make of this? Mr. Friedrich explains that his Valkyries are actually brutal killers whom he envisions flying into action in helicopter gunships of the sort used in the Vietnam War. The program book's prose actually invokes the film ''Apocalypse Now,'' in which such deadly craft figure. Wonderful. Except it is disappointing that all we see in the opera house are eight necrophiliac hoydens flouncing about a morgue in funny clothes, peeking under sheets at dead warriors and stroking cold bodies. Nary a gunship. Evidently a movie buff, Mr. Friedrich also likens Siegfried's appearance in the world of the Gibichungs to a ''Midnight Cowboy'' confronting Manhattan. Doesn't that help you get to the root of ''Gotterdammerung''? I am not unappreciative of Mr. Friedrich's ingenuity or sense of humor. His basic concept - that the gods are a troupe of actors doomed to play out the epic of the ''Ring'' again and again in hopes of someday getting it right - is occasionally stimulating. Like most radical directorial conceits, however, it is impossible to sustain, if only because Wagner's stage directions and libretto insistently reject it. Still, there is something provocative and valid about the circular, Viconian plan that the director devises for this ''Ring,'' a story like ''Finnegans Wake'' without a beginning or an end.

Here again, one is forced to object: Wagner certainly meant the barely perceptible E-flat chording that begins ''Das Rheingold'' to evoke the dawn of time, not a point in a continuum. Mr. Friedrich cannot accept so linear and naive a narrative scheme and insists that Wagner reject it, too. There is more than a hint of arrogance in such an attitude toward art of the past.

There are no heroes in this ''Ring,'' vocally or dramatically. Mr. Friedrich explains in an essay on Siegfried that the musical theater (by which he must also mean the world) no longer needs heroes: ''What it does need is characters that show the contradictions of human greatness, such as Wagner created for us in his sketch of Siegfried.'' It is the duty of the musical stage, therefore, to free Siegfried from ideology: ''Siegfried was a German dream, but the history of the Germans has turned him into a nightmare. Art can help us to understand him anew as a figure closely resembling Faust or Tannhauser. . .'' And so on, quite sensibly.

Fear of the nightmare's recurrence may be why Mr. Friedrich and other German directors have recently chosen to reinvent the ''Ring.'' In explaining it as a timeless theatrical game, he is not so much acting out of boredom with Wagner as distancing himself from a world view that no longer can be accepted. It is only unfortunate that his ''Ring'' requires so many words to tell what should be shown.

Photo of Rene Kollo in the title role of ''Siegfried'' in the German production at the Kennedy Center.