diff --git a/raddb/mods-available/rest b/raddb/mods-available/rest
index 2a1f521ca1d0..33c8d4db090e 100644
--- a/raddb/mods-available/rest
+++ b/raddb/mods-available/rest
@@ -115,7 +115,10 @@ rest {
 	#  - is_json	If true, any nested JSON data will be copied to the attribute
 	#               in string form. Defaults to true.
 	#  - op	        Controls how the attribute is inserted into the target list.
-	#               Defaults to ':='.
+	#               Defaults to ':='. To create multiple attributes from multiple
+	#               values, this should be set to '+=', otherwise only the last
+	#               value will be used, and it will be assigned to a single
+	#               attribute.
 	#  {
 	#      "<attribute0>":{
 	#          "is_json":<bool>,
@@ -124,7 +127,10 @@ rest {
 	#          "value":[<value0>,<value1>,<valueN>]
 	#      },
 	#      "<attribute1>":"value",
-	#      "<attributeN>":[<value0>,<value1>,<valueN>]
+	#      "<attributeN>":{
+	#          "value":[<value0>,<value1>,<valueN>],
+	#          "op":"+="
+	#      }
 	#  }
 
 	#