With Traffic Policy, we automatically parse out useful information from the request’s User-Agent header and make them available as variables. You can use them to deliver tailored content to users based on their browser and device, or to customize or block for SEO crawlers and bots. This rule delivers tailored content to Microsoft Edge users by matching on the req.user_agent.name value. 
on_http_request:
  -     expressions:
      - req.user_agent.name == 'Edge'
    actions:
      -         type: custom-response
        config:
          status_code: 200
          body: Hello Edge User!
You can also quickly block bots from your site by denying them by user-agent using the handy boolean flag. 
on_http_request:
  -     expressions:
      - req.user_agent.is_bot
    actions:
      -         type: deny
        config:
          status_code: 403
Check out the ngrok variable documentation for all the values you can use in your policy.