diff --git a/docs/Model/CreateNotificationSuccessResponse.md b/docs/Model/CreateNotificationSuccessResponse.md
index c130cf7..3167525 100644
--- a/docs/Model/CreateNotificationSuccessResponse.md
+++ b/docs/Model/CreateNotificationSuccessResponse.md
@@ -4,7 +4,7 @@
 
 Name | Type | Description | Notes
 ------------ | ------------- | ------------- | -------------
-**id** | **string** | Notification identifier when the request created a notification. An empty string means no notification was created; read `errors` for details (HTTP may still be 200). | [optional]
+**id** | **string** | Notification identifier when the request created a notification. An empty string means no notification was created; read `errors` for details (HTTP may still be 200). All OneSignal server SDKs expose message-sent / message-not-sent narrowing helpers (named idiomatically per language — e.g. `isMessageSent`, `is_message_sent`, `message_sent?`); prefer them over comparing `id` directly. | [optional]
 **external_id** | **string** | Optional correlation / idempotency-related value from the API response. This is not the end-user External ID used for targeting recipients (that lives under `include_aliases.external_id`). | [optional]
 **errors** | **mixed** | Polymorphic field: may be an array of human-readable strings and/or an object (for example with `invalid_aliases`, `invalid_external_user_ids`, or `invalid_player_ids`) depending on the API response; HTTP may still be 200 with partial success. Typed SDKs model this loosely so both shapes deserialize. | [optional]
 
diff --git a/lib/helpers/NotificationHelpers.php b/lib/helpers/NotificationHelpers.php
index d17345c..d21029f 100644
--- a/lib/helpers/NotificationHelpers.php
+++ b/lib/helpers/NotificationHelpers.php
@@ -74,6 +74,41 @@ public static function createNotificationWithRetry($api, $notification, $maxRetr
         }
     }
 
+    /**
+     * Whether a POST /notifications 200 response is the "message sent" branch.
+     *
+     * POST /notifications returns 200 in two cases that share the
+     * CreateNotificationSuccessResponse shape: a notification was created
+     * (non-empty id), or none was (empty id, with errors carrying the reason).
+     * Prefer this guard over inspecting id directly.
+     *
+     * @param \onesignal\client\model\CreateNotificationSuccessResponse $response
+     *
+     * @return bool true when a notification was created
+     */
+    public static function isMessageSent($response)
+    {
+        if ($response === null) {
+            return false;
+        }
+        $id = $response->getId();
+        return is_string($id) && $id !== '';
+    }
+
+    /**
+     * Whether a POST /notifications 200 response is the "message not sent"
+     * branch -- no notification was created (id absent or empty); inspect
+     * errors for why.
+     *
+     * @param \onesignal\client\model\CreateNotificationSuccessResponse $response
+     *
+     * @return bool true when no notification was created
+     */
+    public static function isMessageNotSent($response)
+    {
+        return !self::isMessageSent($response);
+    }
+
     private static function headerValue($headers, $name)
     {
         if (!is_array($headers)) {
diff --git a/lib/model/CreateNotificationSuccessResponse.php b/lib/model/CreateNotificationSuccessResponse.php
index 3ca89af..1d55a9d 100644
--- a/lib/model/CreateNotificationSuccessResponse.php
+++ b/lib/model/CreateNotificationSuccessResponse.php
@@ -231,7 +231,7 @@ public function getId()
     /**
      * Sets id
      *
-     * @param string|null $id Notification identifier when the request created a notification. An empty string means no notification was created; read `errors` for details (HTTP may still be 200).
+     * @param string|null $id Notification identifier when the request created a notification. An empty string means no notification was created; read `errors` for details (HTTP may still be 200). All OneSignal server SDKs expose message-sent / message-not-sent narrowing helpers (named idiomatically per language — e.g. `isMessageSent`, `is_message_sent`, `message_sent?`); prefer them over comparing `id` directly.
      *
      * @return self
      */