KotlinX Serialization validate input bad json

Question

Let's say I have a Request data class:

data class Request(
   val firstName: String,
   val lastName: String
)

which I want to serialize when getting to a specific api route. Using Ktor, it would look like this:

call.receive<Request>()

This would work perfectly if I get a valid json such as { "firstName: "TestFirst", "lastName": "TestLast" }

But, what if we get a json object or array instead of the expected string? { "firstName: [], "lastName": {} }?

The library would throw an exception and I wouldn't be able to know we had two different validation problems:

1. firstName must be a valid string (and not an array)
2. lastName must be a valid string (and not an object).

How can I find these errors so that I would be able to map them nicely back to the user in the rest api response?