Multiple-attribute contracting allows the alignment of consumers? complex demand profiles and the specific delivery capabilities of suppliers. A two-phased negotiation model is introduced that includes both self-interested negotiations driven by a heuristic strategy and a joint-gains approach to win/win-negotiations. The concept of Pareto-efficiency on imperfect markets (integrative phase) is combined with a strategy-driven, non-altruistic approach to individual utility maximization (distributive phase). The concept of an agent based market is illustrated by grid services as an example negotiation object. The outlined mechanism is evaluated using the "GeneLab" simulation environment that allows to benchmark individual utility gains.