diff --git a/README.md b/README.md
index 1081c580..5f15d45b 100644
--- a/README.md
+++ b/README.md
@@ -84,6 +84,7 @@ The function output is dictated by the function itself.
 | avg()                     | Provides the average value of an array of numbers                   | Double    |
 | stddev()                  | Provides the standard deviation value of an array of numbers        | Double    |
 | length()                  | Provides the length of an array                                     | Integer   |
+| sum()                     | Provides the sum value of an array of numbers                                    | Integer   |
 
 
 Filter Operators