I found following on Wiki to produce PDF out of standalone type(
https://wiki.contextgarden.net/Sharing_graphics):

\starttext
 \startMPpage
  draw fullcircle scaled 10cm ;
 \stopMPPage
\stoptext

It generates a PDF but when I open it with Evince, Evince complains that no
page was found
and does not show anything. Any help would be much appreciated.

-- 
Respect,
Shiv Shankar Dayal