TrAgent is a software-agent based model for a stock exchange such as the New York Stock Exchange and the procedure of trading securities on the trading floor. The model comprises the complete process from the initiation of a trading order until its execution. The software agent paradigm is the framework for implementing the proposed model. The properties of intelligent software agents meet the characteristics of the actors on the trading floor and provide capabilities for efficient distributed computing. Because of the space restriction, the main focus of this paper is on stock broker agent, one of the most important agents in TrAgent. Intelligence is provided to the stock broker agent in order to make reasoning and decisions on the profitability of a firm. This intelligence is provided using Fuzzy Expert System. The paper further discusses the design and development issues concerning different components of the model.