The model can choose to call `whoami`. It cannot choose the subject. The API returns `401` when the bearer is missing or rejected, and `{"subject":"<id>"}` when userinfo accepts it. The tool returns that result to the model.

## What the sample checks

The route depends on `require_auth`. The tool copies `Caller.token` into the `Authorization` header and returns the JSON `subject`, or raises when the response is not successful. `pytest` covers the route and `fetch_subject`. It does not call `Runner`.

That is the whole permission check in the sample. A subject in the tool result means userinfo accepted this token. If you add a tool that refunds an order or deletes a user, that tool's API has to authorize the action. Returning the error string to the model is how the agent learns the call was refused. Swallowing the `401` and inventing a success is the failure mode the docstring is written to prevent.

| Check | Where |
| --- | --- |
| Bearer present and accepted | `GET /whoami`, or whatever route the tool calls |
| Allowed tools for an agent | Trust-store row, if that API enforces it. This sample does not. |
| The action | [Authorization](/docs/concepts/authorization) on the route, after `require_auth` |

Revoke in [Agents](/docs/console/agents) makes the next token exchange fail when the subject is the OIDC client id. The access token already sitting in `Caller` lasts until `expires_in` unless the API rejects it.

When `Caller.token` is an [RFC 8693 token](/guides/agent-delegation), authorize the user in `sub`. The tool does not get to promote the agent to that user.

## Related

| Read | To learn how to |
| --- | --- |
| [Custom channel auth for the OpenAI Agents SDK](/docs/ai/openai-agents/channel-auth) | Put `require_auth` on the route |
| [Enriching instructions for the OpenAI Agents SDK](/docs/ai/openai-agents/enriching-instructions) | Tell the model not to invent a subject |
| [Authorization](/docs/concepts/authorization) | Add the check the next tool needs |
| [LangGraph](/docs/ai/langgraph/authorize-tool-calls) | Apply the same idea inside a graph node |