title: How do I find out what permissions are missing when using Google's API?
body: <p>I have an application that is communicating with Google's partner API to find partnered channels for a CMS. It uses this endpoint <a href="https://developers.google.com/youtube/v3/docs/channels/list" rel="nofollow">https://developers.google.com/youtube/v3/docs/channels/list</a> with the following parameters: <code>GET https://www.googleapis.com/youtube/v3/channels?part=snippet&amp;managedByMe=true&amp;onBehalfOfContentOwner=DMDMbFBm4dizhtG4fvNILQ&amp;key={YOUR_API_KEY}</code></p>
  
  <p>However, it gives me a generic 403 back:</p>
  
  <pre><code>{
   "error": {
    "errors": [
     {
      "domain": "youtube.channel",
      "reason": "channelForbidden",
      "message": "Forbidden",
      "locationType": "parameter",
      "location": "id"
     }
    ],
    "code": 403,
    "message": "Forbidden"
   }
  }
  </code></pre>
  
  <p>Is there any way to debug what is actually missing? Is there a scope missing, or is there something wrong with my account's connection to the content owner? I can successfully retrieve a list over content owners with this endpoint:</p>
  
  <p><code>GET https://www.googleapis.com/youtube/partner/v1/contentOwners?fetchMine=true&amp;key={YOUR_API_KEY}</code></p>
  
  <p>so the connection should be ok. What I'm using are the scopes recommended in the docs, so I'm at my wits end here with just a 403 without any extra information to go on. What else can be wrong?</p>