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(
            "importwallet \"filename\"\n"
            "\nImports keys from a wallet dump file (see dumpwallet). Requires a new wallet backup to include imported keys.\n"
            "\nArguments:\n"
            "1. \"filename\"    (string, required) The wallet file\n"
            "\nExamples:\n"
            "\nDump the wallet\n"
            + HelpExampleCli("dumpwallet", "\"test\"") +
            "\nImport the wallet\n"
            + HelpExampleCli("importwallet", "\"test\"") +
            "\nImport using the json rpc call\n"
            + HelpExampleRpc("importwallet", "\"test\"")
        );
    if (fPruneMode)
        throw JSONRPCError(RPC_WALLET_ERROR, "Importing wallets is disabled in pruned mode");
    LOCK2(cs_main, pwallet->cs_wallet);
    EnsureWalletIsUnlocked(pwallet);
    std::ifstream file;
    file.open(request.params[0].get_str().c_str(), std::ios::in | std::ios::ate);
    if (!file.is_open())
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot open wallet dump file");
    int64_t nTimeBegin = chainActive.Tip()->GetBlockTime();