title: validating Android's authToken on third party server
body: <p>I'm writing an Android application, which uses AccountManager to get the token. From an android app I'm able to interact with Google Picasa - it works fine.</p>
  
  <p>What I would like to achieve is the following: send some text + authToken to my third party server, then check if the token is correct before saving the text. Now the question is: is it possible to determine if the authToken of a particular token is correct solely on the token itself (and maybe email address). </p>
  
  <p>I've already programmed the server part, which accepts the token (send from android application), then issues a request to an URL address:</p>
  
  <pre><code>https://accounts.google.com/o/oauth2/tokeninfo?access_token=%token_here%
  </code></pre>
  
  <p>What I get back is the following JSON:</p>
  
  <pre><code>{
    "error" : "invalid_token"
  }
  </code></pre>
  
  <p>But the link here <a href="http://oauthssodemo.appspot.com/step/4" rel="noreferrer">http://oauthssodemo.appspot.com/step/4</a> states that if a token is correct I should receive a different JSON response. Can you tell me what I'm doing wrong: I believe that the way to check token's validity really isn't that simple, but I should rather implement the whole openid or something. Even if that is the case, how can I check whether the token send by android app is correct, so I can save the 'text' part of the message.</p>
  
  <p>Thank you.</p>