At the moment in the activity chooser in newer versions of Moodle can display a description for activities.
Currently the message for the Attendance activity says that no help is associated with it. I would like to propse that something similar to the following text I lifted from the Wiki page is added to the modulename_help string to describe the activity to users:
The Attendance module is designed for teachers to be able take attendance during class, and for students to be able to view their own attendance record.
A teacher can mark the attendance status of a student as "Present", "Absent", "Late", or "Excused". These status descriptions are configurable, and more can be added. The teacher adds Attendance as an activity of a course, and then sets up the sessions whose attendance is to be tracked.
The Attendance module can generate reports for either the entire class or for individual students. Students may also see their own attendance record if the activity is not hidden.