I'd recommend you can write a small test class which you can run to generate the contract JSON. As a general rule, we also keep the JSON in Git so that we know when it changes (and we have an approval test to manually approve the changes before it gets committed)

Is there an example to generate the contract JSON?

well you need to build a version of the application in order to then sent a request to

Sorry, I am not following - so in this example https://www.http4k.org/guide/modules/contracts/, is there an attribute which I can write as a JSON?

ok - there is an example of what I mean here from http4k-by-example: https://github.com/http4k/http4k-by-example/blob/master/src/test/kotlin/nonfunctional/OpenApiContractTest.kt

Ah, Gotcha - thanks, I will follow this.