The novelty of the evolving electric power industry implies that researchers lack insight into numerous open problems. There is a growing need for advanced modeling approaches that simulate the behavior of electricity markets over time. Accordingly, this article looks at using software agents to help manage the complexity of electricity markets, particularly retail markets, towards ensuring long-term capacity sustainability. The article focuses on bilateral trading and describes some important features of an agent-based system for bilateral contracting with demand response. Special attention is devoted to two strategies for promoting demand response: a "volume management" strategy, for Buyer agents, and a "price management" strategy, for Seller agents.