Asp.net Core Client with Identityserver 3 missing claims - asp.net-web-api

Question

Given:
A JavaScript app that authenticates with oidc over identityerver v3
A Asp.net Core Webapi that authenticates with the given bearer token to identiyserver
The Javascript clients makes calls with the access token itself to the api.
Problem:
The Authentication suceeds but the restored principal is missing some custom claim like "username" and "familyName". I can see that the oidc client in the javascript client has these informations
some claims like "idp" is set in both Javascript and Api Client. But bot are not handled explicitly.
The main difference is that idp is part of the access_token which the username is not.
the configuration of the api is :
JwtSecurityTokenHandler.DefaultInboundClaimTypeMap.Clear();
var authority = config["identity:authority:url"];
app.UseIdentityServerAuthentication(new IdentityServerAuthenticationOptions
{
LegacyAudienceValidation = true,
Authority = authority,
RequireHttpsMetadata = false,
EnableCaching = false,
ApiName = "MyApp.Read",
});
Any hint what i'm missing ? ( I assume it is some kind of profile read in the api?)
Workaround
I extend the configuration with JwtBearerEvents and make a manual read with userclient when the token was authenticated like this
JwtBearerEvents = new JwtBearerEvents
{
OnTokenValidated = async context =>
{
string header = context.Request.Headers["Authorization"];
string accessToken = header.Substring(6);
var result = await userInfoClient.GetAsync(accessToken);
but is this the intended way? Are extended / profile claims meant to be returned only by manually querying them?