diff --git a/api/spec/src/notification/rule.tsp b/api/spec/src/notification/rule.tsp
index e4c086f2e..2940158c7 100644
--- a/api/spec/src/notification/rule.tsp
+++ b/api/spec/src/notification/rule.tsp
@@ -311,5 +311,6 @@ interface Rules {
   @operationId("testNotificationRule")
   test(@path ruleId: ULID): {
     @statusCode _: 201;
+    @body body: Event;
   } | OpenMeter.NotFoundError | OpenMeter.CommonErrors;
 }