Shopify's GraphQL API limits you in complexity (essentially max number of fields returned), but it's basically arbitrary shapes.
Re:Claude Advanced Tool Use
by mattmanser on Monday November 24, 2025 @06:15PM
(#46040554)
OpenAPI does the same thing for http requests, with tooling around it.
With typed languages you can auto-generate OpenAPI schemas from your code.
I would be surprised to see many (or any) GQL endpoints in systems with significant complexity and scale that allow completely arbitrary requests.