title: Alexa, about Discovery of Smart Skill
body: <p>I refer this <a href="https://developer.amazon.com/public/solutions/alexa/alexa-skills-kit/docs/smart-home-skill-api-reference#discovery-messages" rel="nofollow noreferrer">Smart Home Skill API Reference</a>, and implement nodejs lambda function. The document said that if encounter any error when discovering, just response an empty <code>DiscoverAppliancesResponse</code>, and not an error message.</p>
  
  <p>My question is, when <code>accessToken</code> is expired, or in-valid. Then return am empty <code>DiscoverAppliancesResponse</code> too ? Or, any error message about invalid access token, let Alexa server refresh access token.</p>