diff --git a/common/alerting-message/README.md b/common/alerting-message/README.md
index 96d42f3..be89cfb 100644
--- a/common/alerting-message/README.md
+++ b/common/alerting-message/README.md
@@ -29,7 +29,7 @@ Creates a DataDog monitor alert message with the following inputs :
 | append_text | Optional free text string to append to alert | string | `` | no |
 | message_alert | Define a broadcast channel for critical alerts | string | - | yes |
 | message_nodata | Define a broadcast channel for nodata alerts | string | `` | no |
-| message_warning | Define a broadcast channel for warning alerts | string | - | yes |
+| message_warning | Define a broadcast channel for warning alerts | string | - | no |
 | prepend_text | Optional free text string to prepend to alert | string | `` | no |
 
 ## Outputs
@@ -41,3 +41,18 @@ Creates a DataDog monitor alert message with the following inputs :
 ## Related documentation
 
 Datadog notifications official documentation: [https://docs.datadoghq.com/monitors/notifications/?tab=is_alertis_warning](https://docs.datadoghq.com/monitors/notifications/?tab=is_alertis_warning)
+
+## Notes
+
+This module aims to generate a valid message to split notification into different destinations based on its type (alert, warning, no data).
+
+If this way matchs your need so you should be able to use its output alone directly for your monitors.
+You can even use `append_text` and `prepend_text` variables to add context or documentation to monitors.
+
+Else you can still use its output with one or multiple destinations to use it in your own messsage (i.e. with `{{#is_match}}` splitting mechanism).
+
+Here is some tips to understand the behavior of this module and espacially its resulted output:
+* Only `message_alert` is mandatory
+* If `message_warning` or `message_nodata` are not defined it will use `message_alert` by default
+* You can "disable" one notification type by set its variable to empty (i.e. `message_warning = ""`)
+* feel free to use this module multiple times with different combinations to suit your needs
diff --git a/common/alerting-message/inputs.tf b/common/alerting-message/inputs.tf
index 3ebe0cf..60c1305 100644
--- a/common/alerting-message/inputs.tf
+++ b/common/alerting-message/inputs.tf
@@ -6,12 +6,13 @@ variable "message_alert" {
 variable "message_warning" {
   description = "Define a broadcast channel for warning alerts"
   type        = string
+  default     = null
 }
 
 variable "message_nodata" {
   description = "Define a broadcast channel for nodata alerts"
   type        = string
-  default     = ""
+  default     = null
 }
 
 variable "prepend_text" {
@@ -26,3 +27,4 @@ variable "append_text" {
   default     = ""
 }
 
+
diff --git a/common/alerting-message/main.tf b/common/alerting-message/main.tf
index 88d4840..a05c986 100644
--- a/common/alerting-message/main.tf
+++ b/common/alerting-message/main.tf
@@ -10,11 +10,10 @@ EOF
 
   vars = {
     message_alert    = var.message_alert
-    message_warning  = var.message_warning
-    message_nodata   = coalesce(var.message_nodata, var.message_alert)
+    message_warning  = var.message_warning == null ? var.message_alert : var.message_warning
+    message_nodata   = var.message_nodata == null ? var.message_alert : var.message_nodata
     message_recovery = join(" ", compact(distinct(list(var.message_alert, var.message_warning, var.message_nodata))))
     prepend_text     = var.prepend_text
     append_text      = var.append_text
   }
 }
-