A functional requirements document (frd)—also known as a functional requirements specification, functional specification, or functional specification document—is a more. A user requirements document, written by the product manager, is centered around the end user’s needs and expectations for a product.it translates user requirements into. The functional requirements document (frd) is a formal statement of a product's functional requirements. If you are unfamiliar with this document, do not be vexed. The frd is produced by business analysts or sometimes the technical team in response to the business.