Apollo does indeed validate responses as well as requests. If your server tries to send an object that doesn’t match the schema, you’re going to return just a 500 error, which means your clients can trust the graphql types implicitly.

Since in my current job I can’t use graphql but have to type everything in openapi, Had to resort to writing my own lib to get to the same functionality for a REST backend in TS - https://github.com/ovotech/laminar