You can convey quite a bit of information in a task's title, but sometimes that's just not enough.
Task descriptions allow you to add all the detail you (or a teammate) could possibly need.
Add or edit a task's description in Slack
Presently, task descriptions are only visible and editable on Mac or web.
Add or edit a task's description on Mac or web
Click any task, then click the edit button (that'd be the pencil icon).
Add or edit the task's description and click save whenever you're done.