Here is more in-depth API documentation of Microsoft Graph (the underlying API): https://developer.microsoft.com/en-us/graph/docs/concepts/ov...
If you're looking for documentation on the tooling itself, the repo has an overview of how this works and I can provide further context.
Here is the repo if you'd like to self-host the service: https://github.com/microsoftgraph/msgraphql-demo
We're interested in your feedback about integrating with Microsoft Graph using GraphQL. To share your thoughts and scenarios, please leave a comment on UserVoice: https://officespdev.uservoice.com/forums/224641-feature-requ...
I'm happy to answer questions about Microsoft Graph or the implementation of this project.