Can we add more information to the access token response we get during the OAuth flow?

[dan]

We use a standard authorization code grant. We call into /oauth2/token and get back something like this:

{
"access_token":"...",
"expires_in":86399,
"refresh_token":"...",
"token_type":"Bearer",
"userId":"..."
}

We'd like to add some more properties to this JSON response. Is that possible?

[dan]

That response is essentially defined by OAuth2 / OIDC as the token response. If you want to customize it, the best solution is to use a lambda to encode additional details in the access_token (JWT) and then at the client decode that value to extract the necessary claims.

More on lambdas: https://fusionauth.io/docs/v1/tech/lambdas/jwt-populate