alt Hacker NewsI highly suggest you expose functionality through Graphql. It lets users send out an agent with a goal like: "Figure out how to do X" and because graphql has introspection, it can find stuff pretty reliably! It's really lovely as an end user. Best of luck!
A proper REST API would also work without all the extra overhead of GraphQL.
People may dislike XML, but it is easy to make a REST API with and it works well as an interface between computer systems where a human doesn't have to see the syntax.