The sentence "He was tentative" is correct and usable in written English.
Example sentence: When the interviewer asked him if he had any experience, he was tentative with his answer.
Griffith said he was tentative in the ring after the death of Paret.
He was tentative at first, and appeared to be favoring his right side.
He was tentative, lacked aggression and, like most of the other Knicks, deferred in what became deleterious fashion to Ewing.
Pavlik came into the fight intent on matching his usual 100-punches-per-round productivity, but he was tentative early.
But, Mr. Kucinich said, "At the beginning, he was tentative, and he's not at his best when he's tentative".
As a rapper, he's serviceable and deliberate, which means he's tentative.
In the movie, he's tentative, withdrawn, and fascinating in his brooding silence.
Before Wednesday night's game, Joe Torre, the Yankees' manager, talked about how Contreras needed to stay "aggressive; when he's tentative, he's hittable".
You get the sense that he is tentative and unsure of himself or that he is barraged by consultants who tell him this is how he should be.
In his conversations about Vietnam, he is tentative, full of doubt, wary of his military advisers but unwilling to take them on for fear of looking weak.
