Extend the stub agents to handle individual tasks. This usually involves incorporating details of how to interface with some device or program into an agent framework. Test the completed application. Finally, it is one thing to write an application, it is usually quite another to maintain it. This is another place where Mr. Williams' insight is on the mark.
Agents operate in independent threads and communicate only via messages.
From what we have seen, agent programs are easier to maintain precisely because of this separation that protects agents from each other.