I think YAML works fine if you're mapping it into typed data structures, because if you know the target type, you can coerce where possible and fail with an err

I think YAML works fine if you're mapping it into typed data structures, because if you know the target type, you can coerce where possible and fail with an error message otherwise. It can potentially cause a mess if you're using it in a dynamic language, and aren't explicitly coercing/validating the input.