try escaping the asterisk
@@ -50,7 +50,7 @@ allOf:
description: |-
The contents of the messages to be sent. These are arranged in
a map of user IDs to a map of device IDs to message bodies.
- The device ID may also be *, meaning all known devices for the user.
+ The device ID may also be \\*, meaning all known devices for the user.
example: {
"alice@example.org": {
"IWHQUZUIAH": {
