Information should be considered together with the form and materiality of the object. What interaction/function/emotion does it already afford. One memory I have about interacting with a mirror is wiping the steam away to see myself clearly or blowing air onto the surface, write letters and watch it slowly disappear. This could be a trigger of displaying a message, disappearing of a message, an input or something else that makes sense.
Is this a good/useful/informative piece of content to include in the project? Have your say!