The way I had to add a github repo webhook for pull requests

pull_request_webhook.md

This is more complex than necessary.

GitHub webhooks for a URL by default only fire on repo pushes. There appears to be no way in the web UI to set up webhooks for other events. And so we go to the API. I prefer to do this type of thing with Hurl.

• POST to https://api.github.com/repos/:username/:repo/hooks

{
  "name": "web",
  "active": true,
  "events": ["pull_request"],
  "config": {
    "url": "http://example.com/url/path"
  }
}

• GET to https://api.github.com/repos/:username/:repo/hooks to check if the webhook you created has the proper event applied.
• You will see the URL in the admin section of your repo, and you can change it. There will be no mention of what events the URL fires on, but it should stick to pull_request.
• You can use http://requestb.in/ to test the hook.