I need to declare a parameter to store username as input in the first message of dialogflow session, "My name is John" will be the first message the user type to dialogflow cx, I noticed it's not possible to create a parameter on the Start page, is there is a way to detect parameters using EntityType from the first message of the session ?
To detect parameter values from the first end-user input, you can use intent parameters.
First, create an intent and add training phrases like "My name is John" and similar. See how the intent may look like.
Then, add an intent route on the Start page and define agent response in fulfillment. See how the route and a simulator test may look like.
You can also check the general agent design best practices for more information.
