A Functional Specification Developer is responsible for creating detailed, comprehensive documents outlining system requirements, functionalities, and features for a software application or system. This involves understanding user needs, defining system behaviors, and identifying necessary adjustments. They liaise with software developers, stakeholders, and users to ensure the software product aligns with business goals and user expectations. They also contribute to designing, testing, and implementing the software. Their work is crucial in guiding the development process, ensuring that the final product meets the intended purpose and provides a satisfactory user experience.