diff --git a/main.mjs b/main.mjs
index f89b8a6..8334f27 100644
--- a/main.mjs
+++ b/main.mjs
@@ -30,6 +30,14 @@ const grades = [
 	}
 ]
 
+/**
+ * Returns the grade corresponding to mark.
+ *
+ * @param {number} input The marks out of 100.
+ * @return The corresponding grade of the marks.
+ * @customfunction
+ */
+
 function getGrade(mark){
 	if (typeof(mark) != 'number')
 	for (let i=0;i<=grades.length-1;i++){