adjective

acting in a calculating, deceitful way.

a designing little minx

scheming,calculating,conniving,plotting,intriguing,conspiring,cunning,crafty,artful,wily,devious,guileful,canny,shrewd,astute,sharp,insidious,manipulative,treacherous,sly,underhand,deceitful,dishonest,Machiavellian,double-dealing,tricky,crooked,foxy