diff --git a/extensions/functions_string.yaml b/extensions/functions_string.yaml
index 7842e94eb..159988c47 100644
--- a/extensions/functions_string.yaml
+++ b/extensions/functions_string.yaml
@@ -53,6 +53,13 @@ scalar_functions:
       A `start` value of 1 refers to the first characters of the string.  When
       `length` is not specified the function will extract a substring starting
       from position `start` and ending at the end of the string.
+
+      The `negative_start` option applies to the `start` parameter. `WRAP_FROM_END` means
+      the index will start from the end of the `input` and move backwards.
+      The last character has an index of -1, the second to last character has an index of -2,
+      and so on. `LEFT_OF_BEGINNING` means the returned substring will start from
+      the left of the first character.  A `start` of -1 will begin 2 characters left of the
+      the `input`, while a `start` of 0 begins 1 character left of the `input`.
     impls:
       - args:
           - value: "varchar<L1>"
@@ -61,6 +68,9 @@ scalar_functions:
             name: "start"
           - value: i32
             name: "length"
+        options:
+          negative_start:
+            values: [ WRAP_FROM_END, LEFT_OF_BEGINNING, ERROR ]
         return: "varchar<L1>"
       - args:
           - value: "string"
@@ -69,6 +79,9 @@ scalar_functions:
             name: "start"
           - value: i32
             name: "length"
+        options:
+          negative_start:
+            values: [ WRAP_FROM_END, LEFT_OF_BEGINNING, ERROR ]
         return: "string"
       - args:
           - value: "fixedchar<l1>"
@@ -77,24 +90,36 @@ scalar_functions:
             name: "start"
           - value: i32
             name: "length"
+        options:
+          negative_start:
+            values: [ WRAP_FROM_END, LEFT_OF_BEGINNING, ERROR ]
         return: "string"
       - args:
           - value: "varchar<L1>"
             name: "input"
           - value: i32
             name: "start"
+        options:
+          negative_start:
+            values: [ WRAP_FROM_END, LEFT_OF_BEGINNING ]
         return: "varchar<L1>"
       - args:
           - value: "string"
             name: "input"
           - value: i32
             name: "start"
+        options:
+          negative_start:
+            values: [ WRAP_FROM_END, LEFT_OF_BEGINNING ]
         return: "string"
       - args:
           - value: "fixedchar<l1>"
             name: "input"
           - value: i32
             name: "start"
+        options:
+          negative_start:
+            values: [ WRAP_FROM_END, LEFT_OF_BEGINNING ]
         return: "string"
   -
     name: regexp_match_substring