Access Facebook Messenger User Profile API in DialogFlow

You need to make a call to Facebook Graph API in order to get user’s profile.

Facebook offers some SDKs for this, but their official JavaScript SDK is more intended to be on a web client, not on a server. They mention some 3rd party Node.js libraries on that link. I’m particularly using fbgraph (at the time of writing, it’s the only one that seems to be “kind of” maintained).

So, you need a Page Token to make the calls. While developing, you can get one from here:
https://developers.facebook.com/apps/<your app id>/messenger/settings/

Here’s some example code:

const { promisify } = require('util');
let graph = require('fbgraph'); // facebook graph library

const fbGraph = {
  get: promisify(graph.get)
}

graph.setAccessToken(FACEBOOK_PAGE_TOKEN);  // <--- your facebook page token
graph.setVersion("3.2");

// gets profile from facebook
// user must have initiated contact for sender id to be available
// returns: facebook profile object, if any
async function getFacebookProfile(agent) {
  let ctx = agent.context.get('generic');
  let fbSenderID = ctx ? ctx.parameters.facebook_sender_id : undefined;
  let payload;

  console.log('FACEBOOK SENDER ID: ' + fbSenderID);

  if ( fbSenderID ) {
    try { payload = await fbGraph.get(fbSenderID) }
    catch (err) { console.warn( err ) }
  }

  return payload;
}

Notice you don’t always have access to the sender id, and in case you do, you don’t always have access to the profile. For some fields like email, you need to request special permissions. Regular fields like name and profile picture are usually available if the user is the one who initiates the conversation. More info here.

Hope it helps.

Edit

Promise instead of async:

function getFacebookProfile(agent) {
  return new Promise( (resolve, reject) => {
    let ctx = agent.context.get('generic');
    let fbSenderID = ctx ? ctx.parameters.facebook_sender_id : undefined;

    console.log('FACEBOOK SENDER ID: ' + fbSenderID);

    fbGraph.get( fbSenderID )
      .then( payload => {
        console.log('all fine: ' + payload);
        resolve( payload );
      })
      .catch( err => {
        console.warn( err );
        reject( err );
      });
  });
}