diff --git a/docs/smith/font.adoc b/docs/smith/font.adoc
index 2bac8cfb..c7ad44c4 100644
--- a/docs/smith/font.adoc
+++ b/docs/smith/font.adoc
@@ -49,7 +49,7 @@ ap_params::
     Parameters passed to the program that creates the ap database from the source font.
 
 classes::
-    Classes .xml file that adds class information to the attachment point database before conversion into smart font source code.
+	An XML-structured file that allows glyph classes to be defined and then used by both Graphite and OpenType build processes.
 
 no_test::
     If set to True will not include the font in the font tests. This can be set after the font object is created.