why it is not working?

From documentation:

# Name of the desktop file placed by the application in 
# $SNAP_USER_DATA/.config/autostart to indicate that application 
# should be started with the user's desktop session. The application
# is started using the app's command wrapper (<name>.<app>) plus
# any arguments  present in the Exec=.. line inside the autostart
# desktop file.
# (snapd 2.32.4+)
autostart: <command line>

From my yaml:

    command: desktop-launch my-app
    autostart: my-app

From console:

sploid@PC:~/soft/my-app$ snapcraft --version
snapcraft, version 2.43.1
sploid@PC:~/soft/my-app$ snapcraft
Issues while validating snapcraft.yaml: The 'apps/my-app' property does not match the required schema: Additional properties are not allowed ('autostart' was unexpected)

Can someone explain to me why it is not working?