Parse, don't validate (2019)

Please, don't write your own JSON parser/validator. There's JSON Schema https://json-schema.org which has implementations in most languages. You can valiate your JSON by a given, standardized JSON schema file - and you're basically done. After the validation, it's probably good practise to map the JSON to some DTO and may do some further validation which doesn't check the structure of the data but it's meaning.

Json schema doesn't have relation with static type system, ie. in typescript it's much better to use composable, functional combinators at i/o boundaries only and don't do any extra checks anywhere where type system provides guarantees.

I think it's good enough. Besides JSON Schema being a standard instead of custom solution, you also get nice error messages in case there's a validation issue. If your JSON schema file is properly defined it should be safe enough to just map your JSON into some static type DTO afterwards and trust your data and it's types to be valid. In JSON Schema you can validate for strings, numbers, integers, and custom objects. It's quite powerful and - personally - I wouldn't want to implement that kind of stuff on my own.