DecisionNet is a distributed, Web-based electronic market for decision technologies such as data, models, solution algorithms, and modeling environments. Consumer-provider interactions are facilitated by model management software agents provided by DecisionNet. To illustrate different approaches for designing this agent. functionality, we present two agents that embody different designs for mediating consumer and provider interaction with the AMPL and GAMS modeling environments. The AMPL agent is lean, and places significant knowledge and reasoning requirements on both providers (when registering a technology) and consumers (when using technologies). In contrast, the GAMS agent encapsulates knowledge of the GAMS language and modeling environment to facilitate registration of models by providers and to create a run time interface to models for consumers. We discuss the relative advantages of both approaches and argue for the need to incorporate them into environments such as DecisionNet.