What i've seen so far that it was all written on top of plugin as multiline javascript comments like below, and there was no standards like wordpress plugins or so, or did i misunderstand your question?
/*
* Metadata - jQuery plugin for parsing metadata from elements
* Revision: $Id: jquery.metadata.js 3640 2007-10-11 18:34:38Z pmclanahan $
*/
and the description is always told in same way.
/**
* Sets the type of metadata to use. Metadata is encoded in JSON, and each property
* in the JSON will become a property of the element itself.
* * There are three supported types of metadata storage:
* * attr: Inside an attribute. The name parameter indicates *which* attribute.
* class: Inside the class attribute, wrapped in curly braces: { }
* elem: Inside a child element (e.g. a script tag). The
* name parameter indicates *which* element.....
*/