diff --git a/modules/image/image.module b/modules/image/image.module
index 4ca0e34..699a04f 100644
--- a/modules/image/image.module
+++ b/modules/image/image.module
@@ -1070,7 +1070,8 @@ function image_effect_apply($image, $effect) {
 }
 
 /**
- * Returns HTML for an image using a specific image style.
+ * Returns HTML for an image using a specific image style.  This function should
+ * never be called directly, but always as theme('image_style',$variables).
  *
  * @param $variables
  *   An associative array containing:
@@ -1078,12 +1079,12 @@ function image_effect_apply($image, $effect) {
  *   - path: The path of the image file relative to the Drupal files directory.
  *     This function does not work with images outside the files directory nor
  *     with remotely hosted images.
- *   - alt: The alternative text for text-based browsers.
- *   - title: The title text is displayed when the image is hovered in some
- *     popular browsers.
  *   - attributes: Associative array of attributes to be placed in the img tag.
- *   - getsize: If set to TRUE, the image's dimension are fetched and added as
- *     width/height attributes.
+ *   - alt: (optional) The alternative text for text-based browsers.
+ *   - title: (optional) The title text is displayed when the image is hovered
+ *     in some popular browsers.
+ *   - getsize: (optional) If set to TRUE, the image's dimension are fetched and
+ *     added as width/height attributes.
  *
  * @ingroup themeable
  */