The following set of annotated comps represent a small sampling of annotations I regularly write. I prefer to annotate comps as opposed to wires. The reason is that I prefer to work collaboratively with Visual Designers (well truth be told, I prefer to work collaboratively with all roles / crafts), the output of which is comps. Once all design decisions are complete, the Visual Designer typically blows out all final states and breakpoints, and I annotate. 

Note the annotations in red. I cannot find examples anywhere in the world on this wonderful world wide web of how to annotate accessibility considerations. Hence, I created my own system, baking them into my regular annotations. I am sure this is not the only way to write annotations (we all have our ways of working), but this serves as an example for those wishing to learn how to annotate for accessibility.