Annotations are the blueprints for developers. As a designer it is important to give the developer a sense of direction, in their language, as to provide clarity to your mocks. These are some examples previous projects I have designed and the way I annotate my mocks before including them in the tickets I write for our Engineering team to build.
Sometimes some mocks have so many annotations, it can make it hard to see the actual mock so I built a tool that allows the developer to simply scroll up and down to see the annotated view and original view. Here is an example of the tool in action.