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 || request.params.size() > 2)
        throw std::runtime_error(
            "gettransaction \"txid\" ( include_watchonly )\n"
            "\nGet detailed information about in-wallet transaction <txid>\n"
            "\nArguments:\n"
            "1. \"txid\"                  (string, required) The transaction id\n"
            "2. \"include_watchonly\"     (bool, optional, default=false) Whether to include watch-only addresses in balance calculation and details[]\n"
            "\nResult:\n"
            "{\n"
            "  \"amount\" : x.xxx,        (numeric) The transaction amount in " + CURRENCY_UNIT + "\n"
            "  \"fee\": x.xxx,            (numeric) The amount of the fee in " + CURRENCY_UNIT + ". This is negative and only available for the \n"
            "                              'send' category of transactions.\n"
            "  \"confirmations\" : n,     (numeric) The number of confirmations\n"