Copy source of the script to your MATLAB shortcut - e.g. with name Generate Help. Then open your m-file with function and select first line (function declaration with inputs, outputs). Then click on your Generate Help shortcut.
One line bellow first function line will be generated text with template of description.
Example:
========
Selected text:
--------------
function [] = downloadData(name_of_instance)

Created text:
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function [] = downloadData(name_of_instance)
% function [] = downloadData(name_of_instance)
% Function .
%
% INPUT
% name_of_instance [string] ...
%
% OUTPUT
% [] ...
%
% Author: John Smith (john@mail.com)
% Version: 1.0, 20140905
% Changelog:
% 1.0 - first implementation
%