swagger.io - Swagger is an open source RESTapi Documentation Tool.
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Link to QR - Free beautiful QR codes
Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.
Slate API Docs Generator - Create beautiful, intelligent, responsive API documentation.
Slack - A messaging app for teams who see through the Earth!