be too clever by half

be too clever by half

To be too contrived or arrogant in one's cleverness or intelligence, to the point of being irritating to others. Primarily heard in UK. I think every adolescent goes through a stage of being too clever by half, thinking of themselves as the only person who has things really figured out. The phones people use these days are all too clever by half—I can barely even use them to make phone calls!
See also: clever, half