title: HTTP Return Code for "Invalid" Body
body: <p>Let's say I have a REST POST end-point: <code>www.foo.com/validate/X</code> where X represents a number.</p>
  
  <p>My server-side pseudocode looks like this:</p>
  
  <pre><code>validateId(id, jsonObj) { 
  
    if ( isValid(jsonObj) { return 200/OK }
    else { return ??? }
  }
  </code></pre>
  
  <p>What's the right HTTP return code here for the <code>else</code> case? Basically I want to indicate to the client that its <code>jsonObj</code> is not valid.</p>