Looks like the GraphQL beginnings, it feels fresh now and the AI products kind of nudge everything that way but fundamentally the main point is being able to package an API into a standard format, with documented endpoints, support for authentication, and different transports.

Nothing that couldn't be solved by a well designed REST API with Swagger documentation (and authentication, and websockets), but by being the same interface for all APIs it reduces the burden on the LLM.