(a.) Critically discerning; shrewd\; sagacious; subtle; crafty.

Machiavellian Machiavellic acute adroit alert apperceptive appercipient arch argute artful cagey calculating canny clever cogent crafty cunning cute deceitful deep deep-laid designing diplomatic discerning discreet farseeing farsighted feline foreseeing foresighted forethoughted forethoughtful foxy guileful heady incisive ingenious insidious insightful intelligent inventive judicious keen knowing knowledgeable longheaded longsighted observant pawky penetrating perceptive percipient perspicacious perspicuous piercing politic provident prudent quick quick-witted ready resourceful sagacious sage savvy scheming serpentine sharp shifty shrewd slick slippery sly smooth snaky sneaky sophistical stealthy strategic subtile subtle supple tactical trenchant trickish tricksy tricky underhand underhanded understanding vulpine wary wily wise