diff --git a/frameworks/compass/stylesheets/compass/utilities/general/_opacity.sass b/frameworks/compass/stylesheets/compass/utilities/general/_opacity.sass
index 04b85ec4..f8d2a056 100644
--- a/frameworks/compass/stylesheets/compass/utilities/general/_opacity.sass
+++ b/frameworks/compass/stylesheets/compass/utilities/general/_opacity.sass
@@ -1,5 +1,8 @@
-// expects a number from 0 to 1
-=opacity(!opacity = 1)
+//**
+  Provides cross-browser css opacity.
+  @param !opacity
+    A number between 0 and 1, where 0 is transparent and 1 is opaque.
+=opacity(!opacity)
   :opacity= !opacity
   :-moz-opacity= !opacity
   :-khtml-opacity= !opacity