^ Resolved, the problem is there was no

File

type in my schema. I defined one based on this issue (https://github.com/graphcool/framework/issues/1295) and re-tried the POST and now it works. The documentation for the File Management API (https://www.graph.cool/docs/reference/graphql-api/file-management-eer4wiang0/#uploading-workflow) is perhaps a bit misleading, as it says: “Each project contains a file type by default that provides the possibility to add and modify files.” That suggests to me that the File type gets automatically created behind the scenes. Was it supposed to have been?