I use the same info as Chet, including my signature, but also include "original acrylic painting". My reasoning is that there are so many prints on canvas out there now that identifying it as an original is important, and if anyone ever needs to repair or restore or clean the painting, knowing the medium helps them know what methods to use.
There are oil-based Sharpies which are said to be more archival than the ordinary ones. I sign on the back of the canvas, not the stretcher bars, because sometimes canvas needs to be removed and rolled for shipping, then re-stretched (in which case the original bars are not used).
I always staple a business card with my contact information to the stretcher bars or glue it to the hardboard.