diff --git a/api/client-server/v1/rooms.yaml b/api/client-server/v1/rooms.yaml
index 9300d7d1..46273603 100644
--- a/api/client-server/v1/rooms.yaml
+++ b/api/client-server/v1/rooms.yaml
@@ -311,7 +311,12 @@ paths:
                     "user_id": "@alice:example.com"
                   }
                 ],
-                "visibility": "private"
+                "visibility": "private",
+                "private_user_data": [{
+                    "type": "m.tag",
+                    "content": {"tags": ["work"]},
+                    "room_id": "!636q39766251:example.com"
+                }]
               }
           schema:
             title: RoomInfo
@@ -371,6 +376,15 @@ paths:
                 description: |-
                   Whether this room is visible to the ``/publicRooms`` API
                   or not."
+              private_user_data:
+                type: array
+                description: |-
+                  The private data that this user has attached to this room.
+                items:
+                  title: Event
+                  type: object
+                  allOf:
+                    - "$ref": "core-event-schema/event.json"
             required: ["room_id", "membership"]
         403:
           description: >