diff --git a/data/api/client-server/report_content.yaml b/data/api/client-server/report_content.yaml
index d502033f..7afe5cec 100644
--- a/data/api/client-server/report_content.yaml
+++ b/data/api/client-server/report_content.yaml
@@ -178,6 +178,8 @@ paths:
           example: "@someguy:example.com"
           schema:
             type: string
+            format: mx-user-id
+            pattern: "^@"
       requestBody:
         content:
           application/json: