title: What status code to use when a parameter is missing in the query string?
body: <p>I have an endpoint that requires a parameter passed via the query string (is a GET verb).</p>
  
  <p>What is the appropriated status code to give when this parameter is missing from the request? 400 is the one? or should I respond with a 404?</p>
  
  <pre><code>[GET /search?q=ok] =&gt; 200 OK
  [GET /search] =&gt; 400 Bad Request? or 404 Not Found? Or 422 Unprocessable Entity? Others?
  </code></pre>