I want the session to start with the Agent introducing itself and presenting what it can do.

However, when starting adk web I always have to provide the first prompt to get everything going.
I tried returning both a user and assistant message using before agent callback but it even then it only sends the message after the user provides the first prompt.

I did set a state flag so that the "introduction message" would only be sent once , and that part works , but as I am trying to explain, I cannot get it to work so that the Agent starts the chat.

As I am understanding this now, this is mainly an issue with adk web and would be easier to control using other methods (e.g. use the agent with an endpoint)