How do I name a morph?

import { type } from "arktype"

// I have some class that validates or throws. I want to parse an instance of that from a config file.
class ValidatedUserID {
    static fromString(value: string): ValidatedUserID {
        return new ValidatedUserID(value)
    }
    private constructor(readonly data: string) {}
}

const UserID = type("string")
    .describe("a userID")
    .pipe.try(
        ValidatedUserID.fromString
     )
    .describe("No, really, this is a user ID")

const User = type({
    id: UserID
})

const user = User.assert({
    iD: "typo, oops"
})