Writing a dsl, the getters aren't supposed to be used, so I'm writing this at the moment:

var maxGCPauseMillis: Int
            get() = error("invalid")
            set(value) ..

does anyone have a better solution?

why a property? If you have DLS of something that is not supposed to be read, I would expect it to look it like this from the user side:

myDsl {
    maxMillis(20)
}

because I like it more, I find it more readable

What is the harm in reading the value?

no harm, but it's not supposed to be read

found this btw: https://stackoverflow.com/questions/38243085/private-getter-and-public-setter-for-a-kotlin-property

nice idea I found on the youtrack link reported there

var x: Double
        @Deprecated(message = "Write only property", level = DeprecationLevel.HIDDEN)
        get() = error()
        set(value) { source.x = value }

thanks @Joost Klitsie!