diff --git a/x8.md b/x8.md
index 319e97a..0a98124 100644
--- a/x8.md
+++ b/x8.md
@@ -66,6 +66,8 @@ The type `Message` represents a text message exchanged between clients.
 
 Payload is a struct (a compound data type) with the following fields (order is important):
 
+<!-- TODO: Be more precise in struct description, a la RFC, e.g. TLS style https://tools.ietf.org/html/rfc8446 -->
+
 | Field | Name | Type |
 | ----- | ---- | ---- |
 | 1 | text | `string` |