Hi, I read that http4k can generate JSON Schema models (https://www.http4k.org/guide/modules/contracts/) ...is there an example/tutorial for that?

No real tutorial, but you can look at this example https://www.http4k.org/cookbook/typesafe_http_contracts/ or there is a test which shows all of the options (ContractRendererContract)

So, if I understand correctly, the contract allows http4k to validate a request against the "OpenApi" contract, which takes that work away from the developer, right?

http4k will only validate the contents of the path (so it can match the handler) before dispatching the request to the handler. the rest of the parameters are checked only when they are accessed by your code, and the CatchLensFailure filter will convert errors to a 400. so you will have to write zero validation code for any defined "primitives" (including datetimes and anything else the lens API supports).

Ok, thanks for the info.

np