title: Facebook Graph API Messenger integration - The parameter recipient is required
body: <p>I'm trying to create a bot which interacts with Facebook Messenger. I've set up my webhook and can receive messages coming from Facebook. However, when I try to send a message, I get the following error back from Facebook:</p>
  
  <pre><code>{"error":{"message":"(#100) The parameter recipient is required","type":"OAuthException","code":100,"fbtrace_id":"F3iVNecj10i"}}
  </code></pre>
  
  <p>However, I've definitely got the recipient ID in my request. I've sent the request with my bot, cURL and the Chrome Poster extension and get the same result each time. The JSON I send is:</p>
  
  <pre><code>{"recipient":{"id":"XXXXXXXXXXXXXX"},"message":{"text":"hello, world!"}}
  </code></pre>
  
  <p>When using cURL, I took the example directly from the Facebook documentation and send this:</p>
  
  <pre><code>curl -k -X POST -H "Content-Type: application/json" -d '{"recipient":{"id":"XXXXXXXXXXXXXXXX"},"message":{"text":"hello, world!"}}' "https://graph.facebook.com/v2.6/me/messages?access_token=ACCESS_TOKEN"
  </code></pre>
  
  <p>The only difference between this and the example on Facebook is the -k which stops cURL from checking the SSL certificate. I'm tunneling through to my app using ngrok for the incoming messages but sending my requests direct to the Facebook Graph API. The fact that it's happening in my app, cURL and Chrome Poster makes me think that it's something to do with the request (but I can't see what) or my Facebook app setup. Any help is greatly appreciated.</p>