title: RESTful API: require user agent string?
body: <p>My team has a web site with a RESTful API.  We're is working on load testing it, so we've built a small console app to hammer it with requests.  This console app does not set the user agent string, and that is causing an error in our API because it is a required field in our database.</p>
  
  <p>So, should I make the API extra robust and simply use a default string (i.e. "unknown") if a user agent isn't included in the request?  Or, should I return a 400 Bad Request response in this situation?  I know either is possible, but I'm looking for the <em>standard</em> way to do this.</p>