You can write your requirements in any format but a cloud document is the most suitable way from our experience. Here is the template with explanations that you can save to your Google Drive, make edits and then share it with a developer:
https://docs.google.com/document/d/1D0e5djjpaz6yDees_hspsruFJKZggWE8
Yet another great tool for this type of projects is excalidraw.com. What makes it great is that registration is not required. A graphical format allows to quickly and accurately portray all the menus and connections between them, which is enough for simple bots. It can work for more complex bots as well as a part of a technical task that describes only a GUI and logic.