diff --git a/unstable/wlr-output-management-unstable-v1.xml b/unstable/wlr-output-management-unstable-v1.xml
index 411e2f0..a8f4718 100644
--- a/unstable/wlr-output-management-unstable-v1.xml
+++ b/unstable/wlr-output-management-unstable-v1.xml
@@ -191,6 +191,10 @@
         This event describes the physical size of the head. This event is only
         sent if the head has a physical size (e.g. is not a projector or a
         virtual device).
+
+        The physical size event is sent after a wlr_output_head object is created. This
+        event is only sent once per object, and the physical size does not change over
+        the lifetime of the wlr_output_head object.
       </description>
       <arg name="width" type="int" summary="width in millimeters of the output"/>
       <arg name="height" type="int" summary="height in millimeters of the output"/>
@@ -278,6 +282,10 @@
         identify the head by available information from other events but should
         be aware that there is an increased risk of false positives.
 
+        If sent, the make event is sent after a wlr_output_head object is
+        created and only sent once per object. The make does not change over
+        the lifetime of the wlr_output_head object.
+
         It is not recommended to display the make string in UI to users. For
         that the string provided by the description event should be preferred.
       </description>
@@ -302,6 +310,10 @@
         identify the head by available information from other events but should
         be aware that there is an increased risk of false positives.
 
+        If sent, the model event is sent after a wlr_output_head object is
+        created and only sent once per object. The model does not change over
+        the lifetime of the wlr_output_head object.
+
         It is not recommended to display the model string in UI to users. For
         that the string provided by the description event should be preferred.
       </description>
@@ -323,6 +335,10 @@
         available information from other events but should be aware that there
         is an increased risk of false positives.
 
+        If sent, the serial number event is sent after a wlr_output_head object
+        is created and only sent once per object. The serial number does not
+        change over the lifetime of the wlr_output_head object.
+
         It is not recommended to display the serial_number string in UI to
         users. For that the string provided by the description event should be
         preferred.