It is legal to use a description of a copyrighted photo to create an AI-generated photo that is similar to the original, but the commercial sale of such a photo may be infringing on the copyright of the original photo. The copyright law protects the original work of authorship, which includes photos. The use of AI technology to create a similar photo does not negate the copyright protection of the original photo. Therefore, the commercial sale of the AI-generated photo may be considered copyright infringement, unless it falls under the exception of fair use. The fair use exception allows for the use of copyrighted material for certain purposes, such as criticism, commentary, news reporting, teaching, scholarship, or research. However, the commercial sale of the AI-generated photo is unlikely to fall under the fair use exception, and therefore, it may be infringing on the copyright of the original photo. It is recommended to consult with a copyright attorney to determine the legality of using a description of copyrighted photo to create an AI-generated photo for commercial use.