MQL4 ERR_INVALID_TRADE_PARAMETERS
MQL4 error 3 invalid trade parameters maps to ERR_INVALID_TRADE_PARAMETERS: invalid trade parameters. One or more arguments in the trade request are inconsistent with the function, order type, symbol, or current order state. Capture GetLastError immediately after the failed call, correct the cause, and retry only when the condition can change.
Open the Coding Agent, then choose MQL4 from the language menu.
#property strict
#property script_show_inputs
input double Lots = 0.10;
input int Slippage = 3;
void OnStart()
{
if(!IsTradeAllowed())
{
Print("Trading is not currently allowed or the trade context is busy.");
return;
}
RefreshRates();
double price = NormalizeDouble(Ask, Digits);
ResetLastError();
int ticket = OrderSend(Symbol(), OP_BUY, Lots, price, Slippage,
0, 0, "diagnostic", 0, 0, clrNONE);
if(ticket >= 0)
{
Print("Order opened. Ticket ", ticket);
return;
}
int error_code = GetLastError();
Print("OrderSend failed. error=", error_code,
" symbol=", Symbol(), " lots=", DoubleToString(Lots, 2),
" ask=", DoubleToString(price, Digits));
}The official MQL4 runtime table names error 3 ERR_INVALID_TRADE_PARAMETERS and defines it as “invalid trade parameters.” One or more arguments in the trade request are inconsistent with the function, order type, symbol, or current order state.
The error number is evidence about one failed call, not a diagnosis of the whole EA. Read the API sentinel first, then call GetLastError immediately because that function returns the current _LastError value and resets it.
Start with the inputs and external state that existed at the failure point. A later log entry or a successful call can overwrite the useful context.
Do not retry the same parameter set. Correct the invalid field first and submit a new request only if the strategy condition still holds.
Keep the original trading and risk rules intact. A workaround that widens stops, increases volume, changes an account setting, or ignores a failed return value can hide the symptom while changing the system.
| Check | Action |
|---|---|
| Order type, symbol, volume, price, stops, or expiration is invalid | Validate each parameter against the exact trade function contract. |
| A modify or close request uses fields from the wrong selected order | Require successful OrderSelect before using order properties. |
| A multi-symbol EA mixes chart and order symbol properties | Read price and volume properties for the request symbol. |
| The failure log omits the request arguments needed to find the mismatch | Log every material argument and the selected ticket when the call fails. |
The script keeps the OrderSend inputs together and logs the symbol, volume, and price when the call fails. Add the stop, order type, and broker-rule checks required by the real strategy.
The example improves validation and logging. It does not prove the operation will be accepted by a broker or behave safely in live trading.
#property strict
#property script_show_inputs
input double Lots = 0.10;
input int Slippage = 3;
void OnStart()
{
if(!IsTradeAllowed())
{
Print("Trading is not currently allowed or the trade context is busy.");
return;
}
RefreshRates();
double price = NormalizeDouble(Ask, Digits);
ResetLastError();
int ticket = OrderSend(Symbol(), OP_BUY, Lots, price, Slippage,
0, 0, "diagnostic", 0, 0, clrNONE);
if(ticket >= 0)
{
Print("Order opened. Ticket ", ticket);
return;
}
int error_code = GetLastError();
Print("OrderSend failed. error=", error_code,
" symbol=", Symbol(), " lots=", DoubleToString(Lots, 2),
" ask=", DoubleToString(price, Digits));
}Pineify can generate or revise one self-contained .mq4 file with MQL4-specific reference context. Its independent static checker returns MetaEditor diagnostics so you can repair source issues before testing in your own MT4 environment.
Open MQL4 Coding AgentStatic diagnostics do not prove runtime behavior, backtest results, broker compatibility, or live-trading safety.
Check the API return value before interpreting an error number from the log.
Call GetLastError immediately and record error 3, symbol, prices, volume, ticket, and terminal state relevant to the operation.
Validate each parameter against the exact trade function contract.
Compile the revised source, then test with the same MT4 build, broker, symbol, account permissions, and market state.
ERR_INVALID_TRADE_PARAMETERS means invalid trade parameters. The code should still identify which API returned failure and log the inputs used for that call.
Order type, symbol, volume, price, stops, or expiration is invalid A modify or close request uses fields from the wrong selected order A multi-symbol EA mixes chart and order symbol properties The failure log omits the request arguments needed to find the mismatch
Do not retry the same parameter set. Correct the invalid field first and submit a new request only if the strategy condition still holds.
It reports the current _LastError value and resets it. Other operations can change the error state, so a delayed read may describe the wrong call.
Pineify can revise a self-contained .mq4 file, add validation and error logging, and return static MetaEditor diagnostics. It cannot prove broker acceptance, account permissions, market availability, or live execution.
Last verified against the linked official references on . Compile and test the final source in the MetaTrader 4 build, broker, symbol, and account environment you plan to use.
Define the requirement, inspect the generated source, repair diagnostics, and test the behavior in your own MT4 environment.
Open Coding Agent