The idea of writing a scope document can seem like an insurmountable mountain of vagaries and subjective unknowns. There are several resources that talk about the importance of scope, particularly from an agency perspective. The definition of scope really sets the boundaries for the project. No matter how big or small the amount of work the scope allows all of the parties involved to start with a common definition.
Scope is a way for your stakeholders to validate that the requirements have been addressed and added into the scope of work. If something is pulled out of scope it is important to communicate with the stakeholder the rationale behind the exclusion. For example in a recent scope document my teammate and I pulled some work out of the main body of our scope document and added a new section for future considerations. We had already gathered the requirements necessary to complete the work so we left it there for the next round of work.
For the team they get more clarity around the breadth and depth of work that will be included in the project plan. One of the key goals of the team review is to provide an estimate on the work to be done. It is important to keep the team engaged throughout the writing of the document so that they are not blindsided by a something they aren’t expecting. Remember your team is going to be putting fingers on the keyboard you don’t want to alienate them early.
Among the many things the scope document is used for it also serves as a reference when questions come up from stakeholders. Therefore it is important to remove the vagaries and subjective unknowns as much as possible. For example if the stakeholder always uses a certain size for banner ads and always uses flash it would be a good idea to include that. On the other hand if there are no existing mechanisms for their banners this could be an open invitation for interpretation. More definition here may save heartache later on.