Software agents are a major innovation in how people use information systems, and they have parallels with how Decision Support Systems (DSS) support human decision-making. A DSS approach to the development of software agents suggests a highly interactive and flexible interface between the agent and its user, and addresses some potential barriers to the successful adoption of agent technologies. Within a DSS model, agents can be classified as providing search, choice or interface support. Each of these classifications uses techniques originating from separate disciplines and requires different performance measures. We use a real estate agent as a metaphor to examine the descriptive, procedural and semantic knowledge bases that agents can use to support search and choice activities in an e-commerce domain.