The alt text describes what is on the image and the function of the image on the page. Each image should have an alt text. Not just for SEO purposes but also because blind and visually impaired people otherwise will not know what the image is for. Search Engines place a relatively high value on alt texts to determine what is on the image.
Image Alt Text Optimizer automatically syncs daily to ensure all new products have SEO-friendly alt text created. Even better, it does it without any additional work on your part. Just string the text together, and watch ALT Text improve traffic from all the search engines.