They communicate what problem needs. A functional requirements document (frd)—also known as a functional requirements specification, functional specification, or functional specification document—is a more. Are you wondering what a functional requirements document or what an frd is? It allows you to apply a ratings system to your requirements, so you have the visibility (into the value, status, and description of each requirement) that’s. Writing a functional requirements document (frd) is an essential step in the software development process.