diff --git a/message/hal.md b/message/hal.md
index 3249916..88ef860 100644
--- a/message/hal.md
+++ b/message/hal.md
@@ -31,6 +31,8 @@ In our case the "Greeting" resource isn't related to other resources but itself-
 
 It is **customary** for every resource representation to include the `self` link relation. 
 
+> NOTE: The href **MUST** always be **relative path to the API root** (e.g. without the host and scheme).
+
 ## Relation Example
 A more complex document example could be an "Order" resource that has a related resource "Author" (a person who created the order. It might look like: