On the message cookbook page
there are some things misleading:
The wrong image on chapter
shows buttons where should be a dropdown.
The dropdown payload does not work when posted as it is printed in the document, I did not yet find the error.
The Drop selections schema is empty.
The images do not reflect the examples exactly which makes it hard to understand where the values will get shown i the result.
All in all I missed an advice to enclose the 3 lower JSON payloads into the body tag of the first one, otherwise no message content gets created.
With these improvements and the corrected dropdown example, this is a very helpful page!