Intelligent agent-based systems are regarded as the promising technology in bridging the gap between the physical world and cyber-applications. In spite of the rising demands for reusable information systems; current designs are still insufficient in providing efficient reusable mechanisms for system design. One of the major problems hinders the development of information reuse in most traditional systems is the lack of the autonomous character among system modules or subsystems. The emergence of agent technology is able to solve the problem plaguing many traditional systems. Existing agent design models create an agent as a sole system with built-in domain-specific capabilities. However, this design pattern causes several problems while matching and updating agents' capabilities due to the built-in design pattern in these models decreases agents' extensibility, flexibility and reusability. In this paper we introduce a novel design for agent-based systems, which is able to provide an efficient design pattern for improving the reusability, extensibility and flexibility of agent design. The novel agent capability design offers an open and flexible structure; and implements several practical algorithms that can improve the system performance. An experimental program based on several practical cases has been developed to evaluate the performance of the proposed design. The empirical results reveal the efficiency of the new agent design pattern.