TL;DR: if people know what they are supposed to do from the text that fits on a post-it, things are going well - if they don't, the post-its aren't helping, you need more prose than that.
Recently I had the (mis?)fortune of working on a medium-sized (4 man-years) project with a very inexperienced team. I was supposed to be the coding architect supporting them but ended up as the project-manager and tech lead.
When I started in the project (4 months into project calendar time), we had a typical Agile/scrum whiteboard with a bunch of post-its.
There were two problems with that board: 1) even if the post-its moved forward, the project didn't and 2) the developers didn't know what the post-its meant.
To be a bit more concrete, we were supposed to build the back-end of a networked personal video recorder (npvr) for a company that already had one, but one that didn't support variable bandwidth (i.e., mobile). This required knowledge of the existing back-end, systems programming, devops, video transcoding, streaming video protocol and video player functionality - none of which the team had before starting the project. To move the project from the realm of unhappy to the absurd, none of the developers were even familiar with most of the chosen technology stack (Linux, python, RHEL, rpms, zabbix, REST, mpeg4).
So what I ended up doing was abandoning the post-its and moving the project management to a conventional ticket system (JIRA) with signifcant amounts of prose for each ticket - several paragraphs at least, with clear Definitions-of-Done.
If that sounds stupid to you, you have developers who actually know what the customer/client/user wants without excessive prose. Congrats. If they don't, what would you have done?