The most suitable expression to describe the information which a tourist guide (in the US it's a tour guide) gives is in fact commentary: a series of comments, explanations, or annotations. Wikipedia prefers this term in its Audio tour article. The correct verb form is commentate.
An audio tour or audio guide provides a recorded spoken commentary, normally through a handheld device, to a visitor attraction such as a museum. They are also available for self-guided tours of outdoor locations [...] It provides background, context, and information on the things being viewed
However, as worthy alternatives to commentary and commentate, consider:
- The short and to the point information given by the guide was welcomed by the tourists
- The guide explained every historic item we encountered.
Tour guides who work in a stationary setting, such as a museum or
landmark, typically conduct several tours a day to different groups of
visitors. They must select the most important and interesting
information about the subject and present it to the visitors in a
simple, yet appealing, way. Often, tour guides must adapt the
information to suit the specific visitors.