`require_auth` tells you who called `SendMessage`. It does not mean that subject may run every task the executor knows how to do. The sample stops once the subject is known and replies with `subject:<id>`.

## What the card scope does

The agent card advertises scope `agent:invoke` on the Authdog security scheme. That is how a client discovers the scope to request. The sample middleware does not read that scope. It admits the call when userinfo accepts the bearer and the payload has a subject.

If a task needs a scope, check it in the executor after `authdog_subject` is on the request. Reject there, before the executor performs the task. A `401` from the middleware means "no accepted bearer." A later refusal means "this subject may not do this."

## What to check next

The [Agents](/docs/console/agents) registry is the next check on that subject when the caller is an agent:

| Control | Effect |
| --- | --- |
| Allowed scopes and tools | Globs on the trust-store row. `*` allows every tool. |
| Trust-store enforce | Your server applies that row. This A2A sample does not. |
| Revoke | New tokens fail when the subject is the OIDC client id. Tokens already issued last until `expires_in` unless you enforce the trust store. |

Apply [authorization](/docs/concepts/authorization) in the executor when the task is yours: a role, a policy, or an AuthZEN decision. The public skill on the card (`whoami`, "Returns the Authdog subject of the caller") describes the sample. It is not an allow list.

A `200` that contains `subject:` means userinfo accepted the bearer. Treat a missing subject, or a task the subject is not allowed to run, as a refusal the caller can see. Do not run the task and hide the denial inside a model reply.

## Related

| Read | To learn how to |
| --- | --- |
| [Custom channel auth for A2A](/docs/ai/a2a/channel-auth) | Put `require_auth` in front of the executor |
| [Enriching instructions for A2A](/docs/ai/a2a/enriching-instructions) | Return the subject without leaking the token |
| [Agents](/docs/console/agents) | Set allowed tools and revoke the identity |
| [Authorization](/docs/concepts/authorization) | Choose the check that runs after identity |