diff --git a/lib/ansible/modules/monitoring/zabbix/zabbix_action.py b/lib/ansible/modules/monitoring/zabbix/zabbix_action.py
index 07361727c98..8c3211f7d46 100644
--- a/lib/ansible/modules/monitoring/zabbix/zabbix_action.py
+++ b/lib/ansible/modules/monitoring/zabbix/zabbix_action.py
@@ -117,6 +117,7 @@ options:
             operator:
                 description:
                     - Condition operator.
+                    - When I(type) is set to C(time_period), the choices are C(in), C(not in).
                 choices:
                     - '='
                     - '<>'