diff --git a/api-ref/source/os-flavor-extra-specs.inc b/api-ref/source/os-flavor-extra-specs.inc
index b478fea3c6c8..4ea220a9f642 100644
--- a/api-ref/source/os-flavor-extra-specs.inc
+++ b/api-ref/source/os-flavor-extra-specs.inc
@@ -48,6 +48,11 @@ Create Extra Specs For A Flavor
 
 Creates extra specs for a flavor, by ID.
 
+.. note:: Please reference:
+  `Compute Flavors
+  <http://docs.openstack.org/admin-guide/compute-flavors.html#extra-specs>`__
+  for available built-in extra specs under ``Extra Specs`` section.
+
 Normal response codes: 200
 
 Error response codes: unauthorized(401), forbidden(403), itemNotFound(404),