Meta AI Studio (https://aistudio.instagram.com) creates custom chatbots from instructions.

The chatbots created can be accessed online and directly in Instagram conversations (smiley icon at the top right in messages) and Messenger (menu > chat with AIs). A gallery of public chatbots is offered.

The creation and editing of the chatbots, based on LLama, is done via text instructions and predetermined blocks to be defined.
A test is proposed before final validation and a verification of the answers to topics that could be problematic is present.

Chatbots can be private, shared with contacts alone, or public.

Free and unlimited with an account on one of Meta’s social networks.