A key advantage of having a new API resource is that the resource *could*
be protected and the response contextual to the requesting client.  A
challenge that exists today with Authorization Server Metadata is that it
doesn't support per-client responses which creates complications with
change management and discovery that would benefit from per-client metadata
values .  Additionally scopes_supported already doesn't support resource
based scopes for use with resource indicator requests without forcing
implementers to construct resource+scope URIs as scope names (e.g
https://app.example/resource-name/scope:read).  We basically need a
audience+resource+scope tuple to fully qualify a grant for a Resource
Authorization Server than can have N resources each with Y scopes which is
what is being proposed in the PR.

-Karl

On Fri, Dec 5, 2025 at 8:20 AM Aaron Parecki <aaron=
[email protected]> wrote:

> For all practical purposes, it is not likely that an enterprise IdP will
> want to publish a list of all possible Resource Authorization Servers and
> scopes that are configured. We do not expect the IdP's Authorization Server
> Metadata to include data from other trust domains.
>
> There is an open issue to discuss how a Client can discover the possible
> Resources it can obtain an ID-JAG for from the IdP:
> https://github.com/oauth-wg/oauth-identity-assertion-authz-grant/issues/52
>
> The current thinking is that this would be better accomplished by defining
> a new API resource at the IdP, analogous to "userinfo", which returns a
> list of resources supported based on the context of the user presented in
> the request. This could then also include the list of scopes per resource.
>
> Aaron
>
>
> On Fri, Dec 5, 2025 at 12:10 AM Judith Kahrer <judith.kahrer=
> [email protected]> wrote:
>
>> Hello,
>>
>> while studying draft 01 of the Identity Assertion JWT Authorization
>> Grant, I started wondering how the fact that the IdP Authorization Server
>> handles scopes for a different trust domain impacts the ecosystem like the
>> authorization server metadata.
>> To my understanding the IdP Authorization Server supports scopes for a
>> different - possibly multiple - trust domains. Doesn't that affect the
>> meaning of the scopes_supported property in the authorization server
>> metadata? Shouldn't the IdP Authorization Server in its authorization
>> server metadata also include which trust domains and what scopes for those
>> trust domains it supports? Currently, section 6 "Authorization Server (IdP)
>> Metadata" only specifies the urn:ietf:params:oauth:token-type:id-jag as
>> a value for identity_chaining_requested_token_types_supported. I get the
>> feeling that this is not enough. What do you think?
>>
>> Best regards,
>> Judith Kahrer
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