As agent systems become more sophisticated, there is a growing need for agent-oriented debugging, maintenance, and testing methods and tools. This paper presents the Tracing Method and accompanying Tracer tool to help verify actual agent behavior in the implemented system against expected (or designed) agent behavior. The Tracing Method captures dynamic run-time data as actual agent behavior, creates modeled interpretations in terms of agent concepts (e.g. beliefs, goals, and intentions), and compares those models to the agent behavior expected by the designer or developer; thereby, gaining insight into both the design and the implemented agent behavior. The Tracer tool can help: (1) determine if agent design specifications are correctly implemented and guide debugging efforts and (2) discover and examine motivations for agent behaviors such as beliefs, communications, and intentions.