Before our first pattern library was released (when we could communicate design through code, and not merely pictures), I often created simple "explainers" to communicate to front-end developers style and layout details.
I always try to take the target audience into account when creating "explainers". As I was conversant in their front-end stack and conventions, I was able to refer to specific markup, SASS variables, and class names.
Here's an example of HealthSparq's mobile web app, from the user account edit screens.
