I have written a chat bot. Do I need to announce its existence on Stack Apps?
No, it is not mandatory to announce your chat bot with a post on Stack Apps.
It is appreciated if you do, specially if your bot is present in public chat rooms and users stumble upon it. See your post as a service to (potential) users inin case of questions / issues / bugs or complaints about your bot.
You can choose to either post under your own account or that of your bot account. In either case make clear you are the owner and therefortherefore responsible for its (re)actions.
Use the app tag if your chatbot operates headless, on a server. Use the script tag if your bot is a User Scriptuserscript that relies on asa browser and a Script Managerscript manager. Add the chat tag as well.
From Etiquette of Screen-scraping Stack Overflow?
Identify yourself. Add something useful to the user-agent (ideally, a link to an URL, or something informational) so we can see your bot as something other than "generic unknown anonymous scraper."
Proper User-Agents are for example: