At a minimum, help text should note this. This is true for things like addwitnessaddress especially.
"\"key\"                (string) The private key\n"
            "\nExamples:\n"
            + HelpExampleCli("dumpprivkey", "\"myaddress\"")
            + HelpExampleCli("importprivkey", "\"mykey\"")
            + HelpExampleRpc("dumpprivkey", "\"myaddress\"")
        );
    LOCK2(cs_main, pwallet->cs_wallet);
    EnsureWalletIsUnlocked(pwallet);
    std::string strAddress = request.params[0].get_str();
    CTxDestination dest = DecodeDestination(strAddress);
    if (!IsValidDestination(dest)) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid Bitcoin address");
    }
    const CKeyID *keyID = boost::get<CKeyID>(&dest);
    if (!keyID) {
        throw JSONRPCError(RPC_TYPE_ERROR, "Address does not refer to a key");
    }
    CKey vchSecret;
    if (!pwallet->GetKey(*keyID, vchSecret)) {
        throw JSONRPCError(RPC_WALLET_ERROR, "Private key for address " + strAddress + " is not known");
    }
    return CBitcoinSecret(vchSecret).ToString();
}
UniValue dumpwallet(const JSONRPCRequest& request)
{
    CWallet * const pwallet = GetWalletForJSONRPCRequest(request);
    if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
        return NullUniValue;
    }
    if (request.fHelp || request.params.size() != 1)