I should mention one caveat to all of this. Businesses that are required to comply but don't have the ability to bring their websites into compliance can provide an accessible alternative to provide the same information, goods, and services that they provide online, like a staffed phone line. The trick, however, is that this option has to provide at least equal access, including in terms of hours of operation. And, as we know, the internet is around 24/7, so good luck with that.
It’s well-known that the Americans With Disabilities Act (ADA) requires brick-and-mortar businesses be accessible to all patrons. This includes considerations like wheelchair accessibility and Braille or large print for blind and low-vision patrons, among other things. The ADA references “public accommodations,” and outlines 12 categories that essentially covers all types of public-facing businesses. However, the legislation does not address public-facing websites.
The words in the tag should be more than a description. They should provide a text equivalent of the image. In other words, the tag should include the same meaningful information that other users obtain by looking at the image. In the example of the mayor’s picture, adding an “alt” tag with the words “Photograph of Mayor Jane Smith” provides a meaningful description.