\setupexternalfigures
  [height=2cm]

\setupblackrules
  [height=2cm]

\def\graph
  {\blackrule}

\setuplayout
  [width=9cm,
   margin=4cm]

\setupcaptions
  [location={outermargin, high},
   width=\marginwidth]

\setupcaptions
  [mf]
  [location=bottom,
   width=\marginwidth]

\definefloat
  [mf]
  [mfs]

\setupfloat
  [mf]
  [criterium=\rightmarginwidth,
   location=inner,
   default=margin]

\starttext
\showframe

\input knuth

\startplacefigure [title=Figure description] \graph[width=3cm] \stopplacefigure
\startplacefigure [title=Figure description] \graph[width=5cm] \stopplacefigure

\startplacemf [title=Short]              \graph[width=2cm]   \stopplacemf
\startplacemf [title=Figure description] \graph[width=4cm]   \stopplacemf
\startplacemf [title=Figure description] \graph[width=4.2cm] \stopplacemf
\startplacemf [title=Figure description] \graph[width=8cm]   \stopplacemf

\stoptext
