diff --git a/doc/manual/builtins.xml b/doc/manual/builtins.xml
index c8470f4986..1f881a9117 100644
--- a/doc/manual/builtins.xml
+++ b/doc/manual/builtins.xml
@@ -364,6 +364,36 @@ x: x + 456
+ builtins.isString
+ e
+
+ Return true if
+ e evaluates to a string, and
+ false otherwise.
+
+
+
+
+ builtins.isInt
+ e
+
+ Return true if
+ e evaluates to a int, and
+ false otherwise.
+
+
+
+
+ builtins.isBool
+ e
+
+ Return true if
+ e evaluates to a bool, and
+ false otherwise.
+
+
+
+
isNull
e