This can be all right if the item is sufficiently trivial, but the MacGuffin is another kettle of fish. If a powerful item is straightforward, it needs to be something where the characters can't use it all the time -- or better yet, can use if only they figure out how. I have a ring that controls water -- how can I defeat the stone golem with it? It can't drown! (Erosion, on the other hand. . . . ) Indeed, this is better even for the trivial items.
Then there are the items of enormous power and potency. But no perversity. They do not act oddly, or unpredictably. The worst one I remember was the sword "Need". It would give a woman whatever skill she most needed. However, never in all the stories that it appeared, did it ever produce the reaction "Why on earth would it think that I need that?" It was chiefly used by a wizard-woman who did not know swordplay, and no story ever opened with her staring at it and wondering why it was no longer giving her the ability to use a sword without knowing how. That would have been a straightforward example even: the sword thought that what she most needed was to stop depending on it and learn how to use a sword on her own. But, no, never. And the possibilities get more interesting from there.
The best magic item I ever read of was in Piers Anthony's Castle Roogna. A ring claimed to be a wishing ring. When you made a wish, it claimed to be working on it. So you went and did it yourself -- and it claimed credit. But -- every wish made on that ring came true, sooner or later. That's the sort of quirk that makes a magic item really worth creating.