You can also generate Javadoc for your classes and methods. EMF uses annotations for this with a certain property key. The easiest way of adding this is again the diagram. Select a class and maintain the documentation in the "GenModel Doc".

The ecore model looks now like the following. The key in the annotation "http://www.eclipse.org/emf/2002/GenModel" is necessary and the key on the details enty must be "documentation".