My main point here is that we currently have to pass accessToken everywhere so the client can retrieve it. We may want to find a way to avoid 'prop drilling.'

One idea is to create a context for every request using AsyncLocalStorage and just insert the accessToken there.

Ex.
const authContext = new AsyncLocalStorage();

function runWithAccessToken(accessToken, callback) {
return authContext.run(accessToken, callback);
}

This would have to be inserted in mcp-server somewhere.
Then, clients would be able to get the access token directly by calling:

export function getAccessToken() {
const store = authContext.getStore();
return store !== undefined ? store : GCLOUD_AUTH;
}

This would require a decent amount of changes. Maybe there's a better approach out there, so I'll leave it up to you to decide whether to fix the 'prop drilling' here or handle it as an action item later.