diff --git a/api/client-server/definitions/room_event_filter.yaml b/api/client-server/definitions/room_event_filter.yaml
index fd3999132..5258ea30a 100644
--- a/api/client-server/definitions/room_event_filter.yaml
+++ b/api/client-server/definitions/room_event_filter.yaml
@@ -19,28 +19,32 @@ allOf:
     lazy_load_members:
       type: boolean
       description: |-
-        If ``true``, the only ``m.room.member`` events returned in
-        the ``state`` section of the ``/sync`` response are those
-        which are definitely necessary for a client to display
-        the ``sender`` of the timeline events in that response.
+        If ``true``, the only ``m.room.member`` events returned
+        are those which are definitely necessary for a client to
+        display the ``sender`` of the timeline events in the response.
         If ``false``, ``m.room.member`` events are not filtered.
         By default, servers should suppress duplicate redundant
         lazy-loaded ``m.room.member`` events from being sent to a given
-        client across multiple calls to ``/sync``, given that most clients
+        client across multiple calls, given that most clients
         cache membership events (see ``include_redundant_members``
         to change this behaviour).
+
+        Only applicable when filtering state events, such as the
+        ``state`` section of a ``/sync`` or ``/messages``.
     include_redundant_members:
       type: boolean
       description: |-
-        If ``true``, the ``state`` section of the ``/sync`` response will
-        always contain the ``m.room.member`` events required to display
-        the ``sender`` of the timeline events in that response, assuming
-        ``lazy_load_members`` is enabled. This means that redundant
-        duplicate member events may be returned across multiple calls to
-        ``/sync``. This is useful for naive clients who never track
+        If ``true``, response will always contain the ``m.room.member``
+        events required to display the ``sender`` of the timeline events
+        in that response, assuming ``lazy_load_members`` is enabled. This
+        means that redundant duplicate member events may be returned across
+        multiple calls to. This is useful for naive clients who never track
         membership data. If ``false``, duplicate ``m.room.member`` events
-        may be suppressed by the server across multiple calls to ``/sync``.
-        If ``lazy_load_members`` is ``false`` this field is ignored.
+        may be suppressed by the server across multiple calls. If
+        ``lazy_load_members`` is ``false`` this field is ignored.
+
+        Only applicable when filtering state events, such as the
+        ``state`` section of a ``/sync`` or ``/messages``.
     not_rooms:
       description: A list of room IDs to exclude. If this list is absent then no rooms
         are excluded. A matching room will be excluded even if it is listed in the ``'rooms'``