diff --git a/changelogs/push_gateway/newsfragments/1968.clarification b/changelogs/push_gateway/newsfragments/1968.clarification
new file mode 100644
index 00000000..5bf945b6
--- /dev/null
+++ b/changelogs/push_gateway/newsfragments/1968.clarification
@@ -0,0 +1 @@
+Document the schema of `PusherData`.
diff --git a/data/api/push-gateway/push_notifier.yaml b/data/api/push-gateway/push_notifier.yaml
index e23d33b0..fda29da7 100644
--- a/data/api/push-gateway/push_notifier.yaml
+++ b/data/api/push-gateway/push_notifier.yaml
@@ -182,9 +182,15 @@ paths:
                             type: object
                             title: PusherData
                             description: |-
-                              A dictionary of additional pusher-specific data. For
-                              'http' pushers, this is the data dictionary passed in at
-                              pusher creation minus the `url` key.
+                              A dictionary of additional pusher-specific data. This
+                              is the `data` dictionary passed in at
+                              [pusher creation](/client-server-api/#post_matrixclientv3pushersset)
+                              minus the `url` key.
+                            properties:
+                              format:
+                                type: string
+                                description: |-
+                                  The format to use for sending notifications.
                           tweaks:
                             type: object
                             title: Tweaks