A Design Specifications Document developer is responsible for creating comprehensive guidelines that detail the requirements and plans for a software or system. They outline the system's functionality, architecture, and interface, along with the necessary hardware and software components. The developer liaises with stakeholders to understand their needs and translate them into technical terms. They also coordinate with designers and engineers to ensure the design aligns with the document. The document assists in maintaining consistency, reducing misunderstandings, and providing a roadmap for the project. Additionally, the developer may review and update the document as project requirements change.