I was at Canva, a fast growing company adding 500 engineers a year, and the tenured engineers were getting hit with a lot of questions and help requests.
I thought about this list a lot, and believe that maintaining adherence to all 10 checklist items will dramatically improve your technical communication in chat apps.
For advice on writing long form communications, my absolute favorite resource is LEADERSHIP LAB: Writing Beyond the Academy[1]. This lecture will cleanse you of all the bad writing ideas you picked up in 12+ years of schooling, and show you actually how to think about professional writing. I've watched it about 4-5 times.