Weather Messenger: How to get API.ai to get response from Yahoo api?

I am creating simple weather Messenger bot. Using api.aifor handling the chat conversations and would like use Yahoo weather api for handling the weather date requests for user.

So far api.ai is working and responding currently but no idea how add 3rd party api?

Code I find to get started:

/*
 * Yahoo weather
 *
 */
/* Webhook for API.ai to get response from the 3rd party API */
app.post('/ai', (req, res) => {
  console.log('*** Webhook for api.ai query ***');
  console.log(req.body.result);

  if (req.body.result.action === 'weather') {
    console.log('*** weather ***');
    let city = req.body.result.parameters['geo-city'];
    let restUrl = 'APPID='+WEATHER_API_KEY+'&q='+city;

    request.get(restUrl, (err, response, body) => {
      if (!err && response.statusCode == 200) {
        let json = JSON.parse(body);
        console.log(json);
        let tempF = ~~(json.main.temp * 9/5 - 459.67);
        let tempC = ~~(json.main.temp - 273.15);
        let msg = 'The current condition in ' + json.name + ' is ' + json.weather[0].description + ' and the temperature is ' + tempF + ' ℉ (' +tempC+ ' ℃).'
        return res.json({
          speech: msg,
          displayText: msg,
          source: 'weather'
        });
      } else {
        let errorMessage = 'I failed to look up the city name.';
        return res.status(400).json({
          status: {
            code: 400,
            errorType: errorMessage
          }
        });
      }
    })
  }

});

via Janis Rozenfelds