Your site would need to have a text only option, with all functionality accessible through a keyboard for visitors with mobility issues. Once you make these and other changes to meet ADA guidelines, your site would need to be tested by a website development company familiar with ADA compliance issues to be sure that visitors who use assistive technology such as screen readers are able to access your web content fully.
For close to seven years, since July of 2010, the United States Department of Justice (DOJ) has talked about issuing regulations specifically about web accessibility. At that time the US Department of Justice (DOJ) began developing accessibility guidelines for public websites under Title III of the Americans with Disabilities Act (ADA). On December 26, 2017, the Department announced that those regulations were officially withdrawn.
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.