You can assign multiple WebHooks to a single account, one WebHook to multiple accounts, or, simply, one WebHook on an individual account. Required parameters are the URL that Context.IO calls when a matching message is found (callback_url) and a URL Context.IO can call should the WebHook fail (failure_notif_url). There are also a number of optional parameters that will filter the messages that you want by specific criteria (as noted above), such as the “to” field (filter_to), “from” field (filter_from) the subject line (filter_subject), and more. You can even create a WebHook that notifies your app when Gmail labels a message as “Important” (filter_new_important). And of course, we have attachment specific WebHooks that will let your application know when a file has been attached to a message (filter_file_name) or if any revisions have been made to a specific file (filter_file_revisions).