AGP

Although Haneda Airport is not served by shinkansen or large JR rail lines, the monorail offers a short, 15-​minute ride to Hamamatsucho station, where you can connect to the JR Yamanote loop, which in turn connects you to all the other major JR stations in Tokyo, including those served by shinkansen.
There is a JR information desk at the entrance to the monorail from Haneda Airport baggage claim that is staffed by super-​sweet personnel who speak and understand English fully. Here, they can exchange your overseas JR voucher for an actual JR rail pass, make shinkansen reservations, and, if your immediate next destination is the shinkansen, provide step-​by-​step directions in English to help you navigate the trek from Haneda to Hamatsucho, and then to the correct shinkansen platforms at either Tokyo or Shinagawa stations.
Therefore, while the monorail itself probably merits 3 stars, because it introduces an extra step to actually get onto a proper JR rail line or the shinkansen, the 5-​star service at the JR rail counter balances things out and merits an overall 4-​star rating.