diff --git a/README.md b/README.md
index 758da3a..30a3d8b 100644
--- a/README.md
+++ b/README.md
@@ -58,6 +58,22 @@ var parsedTorrent = parseTorrent(torrent) // { infoHash: 'xxx', length: xx, anno
 var peerId = new Buffer('01234567890123456789')
 var port = 6881
 
+// optional options dictionary
+var opts = {
+  rtcConfig: {}, // RTCPeerConnection configuration object
+  wrtc: {}, // custom webrtc impl (useful in node.js)
+  getAnnounceOpts: function () {
+    // provide a callback that will be called whenever announce() is called
+    // internally (on timer), or by the user
+    return {
+      uploaded: 0,
+      downloaded: 0,
+      left: 0,
+      customParam: 'blah' // custom parameters supported
+    }
+  }
+}
+
 var client = new Client(peerId, port, parsedTorrent)
 
 client.on('error', function (err) {
@@ -89,6 +105,14 @@ client.complete()
 // force a tracker announce. will trigger more 'update' events and maybe more 'peer' events
 client.update()
 
+// provide parameters to the tracker
+client.update({
+  uploaded: 0,
+  downloaded: 0,
+  left: 0,
+  customParam: 'blah' // custom parameters supported
+})
+
 // stop getting peers from the tracker, gracefully leave the swarm
 client.stop()
 
diff --git a/client.js b/client.js
index 254a63c..650a4ca 100644
--- a/client.js
+++ b/client.js
@@ -21,13 +21,13 @@ inherits(Client, EventEmitter)
  *
  * Find torrent peers, to help a torrent client participate in a torrent swarm.
  *
- * @param {string|Buffer} peerId         peer id
- * @param {Number} port                  torrent client listening port
- * @param {Object} torrent               parsed torrent
- * @param {Object} opts                  options object
- * @param {Number} opts.rtcConfig        RTCPeerConnection configuration object
- * @param {Number} opts.wrtc             custom webrtc implementation
- * @param {Object} opts.getAnnounceOpts  callback to provide data to tracker
+ * @param {string|Buffer} peerId           peer id
+ * @param {Number} port                    torrent client listening port
+ * @param {Object} torrent                 parsed torrent
+ * @param {Object} opts                    options object
+ * @param {Number} opts.rtcConfig          RTCPeerConnection configuration object
+ * @param {Number} opts.wrtc               custom webrtc impl (useful in node.js)
+ * @param {function} opts.getAnnounceOpts  callback to provide data to tracker
  */
 function Client (peerId, port, torrent, opts) {
   var self = this