I have a font that already comes with a smallcaps variant.

How do I define it?

I've tried the following, which I think should work from the documentation I've seen, but doesn't:

\starttypescript[serif]                           [garamond]
   \definefontsynonym[Serif]                   [file:/home/joel/.fonts/12/EBGaramond-Regular.otf]
   \definefontsynonym[SerifBold]               [file:/home/joel/.fonts/12/EBGaramond-Bold.otf]
   \definefontsynonym[SerifItalic]               [file:/home/joel/.fonts/12/EBGaramond-Italic.otf]
   \definefontsynonym[SerifBoldItalic]           [file:/home/joel/.fonts/12/EBGaramond-BoldItalic.otf]
   \definefontsynonym[SerifCaps]               [file:/home/joel/.fonts/13/EBGaramond12-AllSC.otf]
\stoptypescript

\starttypescript[sans]                           [garamond]
   \definefontsynonym[Sans]                   [file:/home/joel/.fonts/12/EBGaramond-Regular.otf]
   \definefontsynonym[SansBold]               [file:/home/joel/.fonts/12/EBGaramond-Bold.otf]
   \definefontsynonym[SansItalic]               [file:/home/joel/.fonts/12/EBGaramond-Italic.otf]
   \definefontsynonym[SansBoldItalic]           [file:/home/joel/.fonts/12/EBGaramond-BoldItalic.otf]
   \definefontsynonym[SansCaps]               [file:/home/joel/.fonts/13/EBGaramond12-AllSC.otf]
\stoptypescript

\starttypescript[garamond]
   \definetypeface[garamond]                   [rm][serif][garamond][default]
   \definetypeface[garamond]                   [ss][sans][garamond][default]
   \definetypeface[garamond]                   [mm][math][modern][default]
\stoptypescript

\starttext

   This is regular text.

   {\smallcaps This should be in smallcaps.}

   {\WORD This should be regular text, but capitalized, not really smallcaps.}

\stoptext

--Joel