How it is different then calling getAuthenticatedUser()?

  async getAuthenticatedUser(): Promise<string | null> {
    try {
      return await requireAuth(await this.resolveOptions());
    } catch (e) {
      return null;
    }
  }

Correct me if I am wrong

It sounds like getAuthenticatedUser() currently returns:

• string for firebase login
• null for gcloud auth application-default login
• Throw error if there is neither

Should we document that clearly in requireAuth().

Maybe change this.getAuthenticatedUser() to encode that information property

requireAuth can return null when you are authenticated via a service account, but it errors when the user is not authenticated. getAuthenticated catches those errors and returns null. Under the previous logic, this triggered the conditional that returned mcpAuthError()

Good call - refactored this. Now, getAuthenticatedUser() returns:
email for firebase login
'Application default credentials when using ADC
null for gcloud auth application-default login

and we skip the redundant requireAuth call.

nit: "Application Default Credentials"

Could you also update the tsdoc on requireAuth? It wasn't obvious what null means reading it.

Thanks!