7.1.2 Command Documentation

Command documentation is a description of what the command does when it is invoked as an extended command or from a key. Command documentation may be either a string or a function. If the documentation is a string then the first line should briefly summarize the command, with remaining lines filling the details. Example:

(defcommand "Forward Character" (p)
  "Move the point forward one character.
   With prefix argument move that many characters, with negative
   argument go backwards."
  "Move the point of the current buffer forward p characters."
   . . .)

Command documentation may also be a function of one argument. The function is called with either :short or :full, indicating that the function should return a short documentation string or do something to document the command fully.