The Collaborative International Dictionary of English v.0.48:

Amenableness \A*me"na*ble*ness\, n.
   The quality or state of being amenable; liability to answer
   charges; answerableness.
   [1913 Webster]

WordNet (r) 3.0 (2006):

amenableness
    n 1: the trait of being cooperative [syn: amenability,
         amenableness, cooperativeness]