This is a very powerful approach because there are json schema libraries available in all major languages. TypeScript is a better source for truth because it ca

This is a very powerful approach because there are json schema libraries available in all major languages. TypeScript is a better source for truth because it can represent things json schema can't. It is possible to generate a json schema from a TypeScript definition (see https://github.com/YousefED/typescript-json-schema https://github.com/YousefED/typescript-json-schema), which means TypeScript can be the single source of truth for API definitions, be used directly in the frontend and, in json schema form, used to test directly against API responses.