The Collaborative International Dictionary of English v.0.48:

Artfulness \Art"ful*ness\, n.
   The quality of being artful; art; cunning; craft.
   [1913 Webster]

WordNet (r) 3.0 (2006):

artfulness
    n 1: the quality of being adroit in taking unfair advantage
         [ant: artlessness]

Moby Thesaurus II by Grady Ward, 1.0:

147 Moby Thesaurus words for "artfulness":
   Gongorism, Italian hand, ability, acuteness, address, adeptness,
   adroitness, affectation, affectedness, airmanship, animal cunning,
   art, artifice, artificiality, artisanship, artistry, astuteness,
   bravura, brilliance, cageyness, callidity, canniness, capability,
   capacity, cleverness, command, competence, control, coordination,
   craft, craftiness, craftsmanship, credibility gap, cunning,
   cunningness, deceit, deceitfulness, deftness, deviousness,
   dexterity, dexterousness, dextrousness, diplomacy,
   disingenuousness, duplicity, efficiency, euphemism, euphuism,
   expertise, facility, falseheartedness, falseness,
   fine Italian hand, finesse, forswearing, foxiness, fraud,
   furtiveness, gamesmanship, grace, grip, guile, guilefulness,
   handiness, horsemanship, hyperelegance, hypocrisy, indirection,
   ingeniousness, ingenuity, insidiousness, insincerity, intrigue,
   inventiveness, know-how, low cunning, manneredness, mannerism,
   marksmanship, mastership, mastery, one-upmanship, overelaboration,
   overelegance, overniceness, overrefinement, pawkiness, perjury,
   practical ability, preciosity, preciousness, pretentiousness,
   proficiency, prowess, purism, quickness, readiness, resource,
   resourcefulness, satanic cunning, savoir-faire, savvy, seamanship,
   sharp practice, sharpness, shiftiness, shrewdness, skill,
   skillfulness, slickness, slipperiness, slyness, sneak attack,
   sneakiness, sophistry, stealth, stealthiness, style, subtility,
   subtilty, subtleness, subtlety, suppleness, surreptitiousness,
   tact, tactfulness, technical brilliance, technical mastery,
   technical skill, technique, timing, treacherousness, trickiness,
   uncandidness, uncandor, underhandedness, unfrankness,
   unnaturalness, unsincereness, untruthfulness, virtuosity, wariness,
   wiles, wiliness, wit, wizardry, workmanship