Hypothetical way of manifesting Web Intents for a service to the browser, along with some facility for property name mapping and proprietary requirements.

intents.manifest.json

{
  'vendor': 'twitter',
  'intents': [
    {
      'name': "Follow",
      'verb': 'follow',
      'url': 'http://twitter.com/intent/follow',
      'required_params': ['screen_name'],
      'param_map': {
        'user_name': 'screen_name'
      }
    },
    {
      'name': "View Profile",
      'verb': 'profile',
      'url': 'http://twitter.com/intent/user',
      'required_params': ['screen_name'],
      'param_map': {
        'user_name': 'screen_name'
      }
    },
    {
      'name': "Tweet",
      'verb': 'post',
      'url': 'http://twitter.com/intent/tweet'
    },
    {
      'name': "Tweet Link",
      'verb': 'share',
      'required_params': ['url'],
      'url': 'http://twitter.com/share'
    },
    {
      'name': "Retweet",
      'verb': 'share',
      'required_params': ['tweet_id'],
      'url': 'http://twitter.com/intent/retweet',
      'param_map': {
        'object_id': 'tweet_id'
      }
    },
    {
      'name': "Reply to Tweet",
      'verb': 'reply',
      'url': 'http://twitter.com/intent/tweet',
      'required_params': ['in_reply_to'],
      'param_map': {
       'parent_id': 'in_reply_to'
      }
    },
    {
      'name': "Favorite",
      'verb': 'save',
      'url': 'http://twitter.com/intent/favorite',
      'required_params': ['tweet_id'],
      'param_map': {
       'object_id': 'tweet_id'
      }
    },
    {
      'name': "Direct Message",
      'verb': 'post',
      'url': 'http://twitter.com/intent/message',
      'required_params': ['screen_name'],
      'param_map': { 'user_name': 'screen_name' }
    },
  ]
}