A Functional spec developer is responsible for creating functional specifications, which are detailed descriptions of system's capabilities, appearance, and interactions. They analyze end-user needs and define system functionality, serving as a bridge between users and technical developers. They document processes, articulate requirements, and ensure that the final product aligns with user expectations. Their work involves collaboration with various stakeholders, including project managers, designers, and developers, to ensure that the software solution meets user needs, is technically feasible, and can be feasibly integrated into the existing system. They may also participate in user acceptance testing.