You can also use github.com/ibm/openapi-to-graphql to build a GraphQL interface using your REST APIs. In addition to taking a data centric approach, it allows for linking resources within and across APIs, and if you want to customize a particular resolver you can do so. It works with swagger and Open API Specification 3.0.
(This article was updated July 2018. We’ve included new information on acquisitions, funding rounds, business model pricing, and instructor pay. Let me know in the comments if you have any questions.)