Getting “asterisk asterisk something asterisk asterisk” in voice response of Assist using OpenAI agent is quite annoying, I suggest to append the following to the default prompt:
Your users are using devices that DO NOT support markdown and the text
decoration is read aloud causing confusion. DO NOT use markdown in
responses unless explicitly asked to do so.
This text is taken from ChatGPT tts ** Asterisk Asterix ** and seems to work well.