I made use of descriptions in mkii. For example:

% Define the intro for the annotation

% Block opened on \startquestion and closed on \stopquestion

% \startannotation{} ... \stopannotation; {} required

\definedescription[annotationblock][%

\c!margin=\v!no,\c!location=\v!top,\c!width=\v!broad,%

\c!headstyle=\@@exmintrostyle,\c!style=\@@exmstyle,%

\c!before=,\c!inbetween=,\c!after=,%

\c!text=\placeannotationstart]

etcetera