What did Toriyama actually do on Dragon Ball GT?
Dragon Ball GT premiered on Fuji TV on February 7, 1996, exactly one week after Dragon Ball Z ended, and ran 64 episodes to November 19, 1997. It is the only Dragon Ball television series that adapts no manga, because there was none: Toriyama had ended his 519 chapters the year before and declined to draw a sequel. Toei Animation conceived the continuation itself, sending Goku, turned back into a child by the Black Star Dragon Balls, across the galaxy with Pan and Trunks.
Toriyama's contribution was real, front loaded, and specific. Producer Kozo Morishita's account of the process is the clearest record: Toei's simple plot outlines, of the kind that said only which types of planets the cast would visit, were handed to Toriyama, and he drew the new character drafts and image illustrations in response: child Goku, Pan, Trunks, the newcomer robot Giru, and the Capsule Corp spaceship, along with designs for much of the main cast and a later drawing of Super Saiyan 4 Goku for the series' home video box. The title was his too. Morishita recalled that the staff received only the name GT and had to look up what it could mean, settling on Grand Touring, a road movie across the universe; reference works render his intent as Grand Tour. He also drew the series logo.
Then he stepped back and watched it as a viewer. His settled verdict, given for the series' DVD box, is the sentence every argument about GT eventually quotes: he called it a grand side story of the original Dragon Ball, praised the animators as excellent, and singled out character designer Katsuyoshi Nakatsuru for working well inside his style. He never wrote an episode, never drew a GT manga, and never pronounced the word canon, a term he generally left to others. The accurate summary is the division of labor itself: Toei invented the journey, Toriyama dressed it, named it, and blessed it as a side story, which is neither the authorship fans sometimes claim for him nor the absence they sometimes claim against the show.