At a minimum, help text should note this. This is true for things like addwitnessaddress especially.
{
    CWallet * const pwallet = GetWalletForJSONRPCRequest(request);
    if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
        return NullUniValue;
    }
    if (request.fHelp || request.params.size() != 1)
        throw std::runtime_error(
            "dumpprivkey \"address\"\n"
            "\nReveals the private key corresponding to 'address'.\n"
            "Then the importprivkey can be used with this output\n"
            "\nArguments:\n"
            "1. \"address\"   (string, required) The bitcoin address for the private key\n"
            "\nResult:\n"