diff --git a/functions/_shade.scss b/functions/_shade.scss
index 0fb025d..aa39d87 100644
--- a/functions/_shade.scss
+++ b/functions/_shade.scss
@@ -1,12 +1,12 @@
-/* Yanked from http://sass-guidelin.es/#lightening-and-darkening-colors */
+/* Inspired by http://sass-guidelin.es/#lightening-and-darkening-colors */
 
 /*
 Slightly darken a color
 @access public
 @param {Color} $color - color to shade
-@param {Number} $percentage - percentage of `$color` in returned color
+@param {Number} $percentage [50%] - percentage of `$color` in returned color
 @return {Color}
 */
-@function shade($color, $percentage) {
+@function shade($color, $percentage: 50%) {
   @return mix(black, $color, $percentage);
 }
diff --git a/functions/_tint.scss b/functions/_tint.scss
index e7e4329..29f1027 100644
--- a/functions/_tint.scss
+++ b/functions/_tint.scss
@@ -1,12 +1,12 @@
-/* Yanked from http://sass-guidelin.es/#lightening-and-darkening-colors */
+/* Inspired by http://sass-guidelin.es/#lightening-and-darkening-colors */
 
 /*
 Slightly lighten a color
 @access public
 @param {Color} $color - color to tint
-@param {Number} $percentage - percentage of `$color` in returned color
+@param {Number} $percentage [50%] - percentage of `$color` in returned color
 @return {Color}
 */
-@function tint($color, $percentage) {
+@function tint($color, $percentage: 50%) {
   @return mix(white, $color, $percentage);
 }