Access token jwt format


I am new to auth0 so I have a problem and I am sure ~I am missing something.

So here it is. I created a regular web app and managed to get authentication going by redirecting user to sign in and then redirecting back to mydomain.callback with a code as a query parameter. Now using this code I make an api call to my web app and then in the contoller method of my web app I use the code and send a post request to token url to echange the code with tokens. Also note that I created an api resource from the aPIs section in auth0 dashboard. in the post request I use the client id, client secret, grant type to authorization code, audience to the indentifier of the api I created earlier, the code set to whatever the code in the query parameter from the first round when user authenticates, and a redirect url which is the same as previously. I get only the access token in the opaque format even though I set the audience. If I change to client credentiuals I noticed that I get the access token in the jwt format. I also noticed that from the api dashboard that I can only use client credentials to exchange tokens (see image below)?

Why is that?

I just found a selution to my problem actually. I was including the audience parameter in the token exchange api call but not in the initial call of the code flow when redirecting user to authenticate. By includeding audience as a query parameter there fixed the issue for me!