GraphQL
New
hold
Blurb
The query language for modern APIs.
Summary
Published by Facebook in 2015, it solves a problem that is unique to them that really only existed for a short period of time. Namely, requests were coming in so fast that it was wasting a lot of bandwidth, since not all clients needed the same information.
OpenAPI is a much lighter weight solution, which solves far more use-cases, until you really do hit the hyper-scale of Facebook. Until you do it is best if you avoid GraphQL.