As per the title. Currently only built-in scripts have description.
update the script with metadata
# --- Start MAAS 1.0 script metadata ---
# name: 01-node-01-update
# title: Node update
# description: This is my script desc
# type: commissioning
# script_type: commissioning
# tags: commissioning
# recommission: True
# destructive: False
# hardware_type: node
# --- End MAAS 1.0 script metadata ---