mql5-skills/skills/mql5/SKILL.md

name, description, version, license, compatibility, metadata

name	description	version	license	compatibility	metadata
mql5	MQL5 development skill for MetaTrader 5 Expert Advisors, Indicators, Scripts, and Services. Focus on positions, orders, indicators, ticks, bars, risk management, backtesting, and multi-instance MT5 operations. Includes programming book and API reference documentation.	0.1	MIT	Target: MetaTrader 5 platform. Language: MQL5 (C++-like syntax). File extensions: *.mq5 (source), *.mqh (headers). Run time: Windows native, Linux via Wine, macOS via Wine.	project-version focus-areas 0.1.0 positions orders indicators ticks bars risk-management backtesting

MQL5 Development Skill

Expert development skill for MetaTrader 5. Covers EA, Indicator, Script, and Service creation with emphasis on trading operations, technical indicators, multi-timeframe analysis, risk management, and backtesting workflows.

1. MQL5 Fundamentals

Language and File Types

• MQL5 syntax is similar to C++ but with domain-specific additions
• Source files: *.mq5 (programs), *.mqh (headers)
• Compiled output: *.ex5 (same name as source)
• Compiler: built into MetaEditor IDE

Program Types

Type	Purpose	Key Handler	Directory
Expert Advisor	Automated trading	OnTick()	MQL5/Experts/
Indicator	Technical analysis	OnCalculate()	MQL5/Indicators/
Script	One-shot execution	OnStart()	MQL5/Scripts/
Service	Background task	OnStart() + OnTimer()	MQL5/Services/

MQL5 Directory Structure

Default locations per platform:

Platform	Path
Windows 10+	$env:USERPROFILE\AppData\Roaming\MetaQuotes\Terminal\$INSTANT_HEX\MQL5
Linux (Wine)	~/.wine/drive_c/Program Files/MetaTrader 5/MQL5/
macOS	Unknown — verify per installation

Key subdirectories:

MQL5/
├── Experts/          # EA source files (.mq5)
│   ├── Examples/     # Built-in example EAs
│   └── Free Robots/  # Downloaded EAs
├── Indicators/       # Indicator source files
├── Scripts/          # Script source files
├── Services/         # Service source files
├── Include/          # Header files (.mqh)
│   ├── Trade/        # Trading classes (Trade.mqh, PositionInfo.mqh, etc.)
│   ├── Indicators/   # Indicator helpers
│   ├── Expert/       # Expert base classes
│   └── Generic/      # Generic collections
├── Files/            # File I/O sandbox
├── Images/           # Image resources
├── Libraries/        # DLL/shared libraries
├── Profiles/         # Chart profiles
└── Logs/             # Log files

Multi-Instance MT5

Multiple MT5 instances can run simultaneously for different accounts:

1. Install MT5 to separate target paths (e.g. MT5_BrokerA/, MT5_BrokerB/)
2. Each instance has its own MQL5/ directory
3. To identify which account an instance is logged into:
   • AccountInfoInteger(ACCOUNT_LOGIN) — account number
   • AccountInfoString(ACCOUNT_NAME) — account name
   • AccountInfoString(ACCOUNT_SERVER) — broker server
4. Each instance runs as a separate process — use Magic Number to distinguish EA trades across instances on the same symbol

2. Trading Operations

Core Concepts

• Order: instruction to buy/sell (Market or Pending)
• Deal: executed exchange (buy at Ask, sell at Bid)
• Position: current obligation (long or short)

CTrade Class (Standard Library)

#include <Trade\Trade.mqh>

CTrade trade;

// Setup in OnInit()
trade.SetExpertMagicNumber(EA_MAGIC);
trade.SetMarginMode();
trade.SetTypeFillingBySymbol(Symbol());
trade.SetDeviationInPoints(Slippage);

Key methods:

Method	Purpose
PositionOpen(symbol, type, volume, price, sl, tp)	Open a position
PositionClose(symbol, deviation)	Close a position
PositionModify(symbol, sl, tp)	Modify SL/TP
PositionClosePartial(symbol, volume)	Partial close
Buy(volume, price, sl, tp, comment)	Shortcut for buy
Sell(volume, price, sl, tp, comment)	Shortcut for sell
BuyLimit/BuyStop/SellLimit/SellStop(...)	Pending orders
ResultRetcode()	Check trade server return code
ResultDeal()	Get deal ticket after execution

Position Queries

// Iterate open positions (Hedging account)
uint total = PositionsTotal();
for (uint i = 0; i < total; i++) {
    string sym = PositionGetSymbol(i);
    if (sym == _Symbol && PositionGetInteger(POSITION_MAGIC) == EA_MAGIC) {
        double vol = PositionGetDouble(POSITION_VOLUME);
        double sl  = PositionGetDouble(POSITION_SL);
        double tp  = PositionGetDouble(POSITION_TP);
        long   type = PositionGetInteger(POSITION_TYPE);
    }
}

// Netting account — simpler
if (PositionSelect(_Symbol)) {
    // position is selected
}

Order Execution Pattern

// Calculate price
double price = (signal == ORDER_TYPE_BUY)
    ? SymbolInfoDouble(_Symbol, SYMBOL_ASK)
    : SymbolInfoDouble(_Symbol, SYMBOL_BID);

// Open with SL/TP
trade.PositionOpen(_Symbol, signal, lotSize, price, sl, tp, "EA Signal");

// Always check result
if (trade.ResultRetcode() != TRADE_RETCODE_DONE) {
    Print("Trade failed: ", trade.ResultRetcode());
}

Hedging vs Netting

bool IsHedging = ((ENUM_ACCOUNT_MARGIN_MODE)
    AccountInfoInteger(ACCOUNT_MARGIN_MODE) == ACCOUNT_MARGIN_MODE_RETAIL_HEDGING);

• Hedging: multiple positions per symbol, must iterate and match Magic Number
• Netting: one position per symbol, use PositionSelect()

3. Indicators and Multi-Timeframe

Built-in Indicator Handles

// Moving Average
int handle = iMA(_Symbol, PERIOD_H1, 50, 0, MODE_SMA, PRICE_CLOSE);

// RSI
int handle = iRSI(_Symbol, PERIOD_H1, 14, PRICE_CLOSE);

// MACD
int handle = iMACD(_Symbol, PERIOD_H1, 12, 26, 9, PRICE_CLOSE);

// Bollinger Bands
int handle = iBands(_Symbol, PERIOD_H1, 20, 0, 2.0, PRICE_CLOSE);

Reading Indicator Values

double buffer[];
ArraySetAsSeries(buffer, true);
if (CopyBuffer(handle, 0, 0, 3, buffer) != 3) {
    Print("No indicator data");
    return;
}
// buffer[0] = current bar value
// buffer[1] = previous bar value

Multi-Timeframe Analysis

// Higher timeframe trend
int h4_ma = iMA(_Symbol, PERIOD_H4, 50, 0, MODE_SMA, PRICE_CLOSE);

// Entry timeframe signal
int h1_rsi = iRSI(_Symbol, PERIOD_H1, 14, PRICE_CLOSE);

// In OnTick():
double h4_val[], h1_val[];
CopyBuffer(h4_ma, 0, 0, 1, h4_val);
CopyBuffer(h1_rsi, 0, 0, 1, h1_val);

bool bullish = (SymbolInfoDouble(_Symbol, SYMBOL_BID) > h4_val[0]);
bool oversold = (h1_val[0] < 30);

New Bar Detection

datetime lastBarTime = 0;

void OnTick() {
    datetime currentBarTime = iTime(_Symbol, _Period, 0);
    if (currentBarTime == lastBarTime) return;  // not a new bar
    lastBarTime = currentBarTime;
    // New bar — run analysis here
}

4. Ticks and Bars

Timeseries Access

Index 0 = current (unfinished) bar. Array is reverse-ordered.

MqlRates rates[];
ArraySetAsSeries(rates, true);
CopyRates(_Symbol, _Period, 0, 100, rates);

// rates[0] = current bar
// rates[1] = previous bar
// rates[0].open, .high, .low, .close, .tick_volume, .time

Tick Data

MqlTick tick;
SymbolInfoTick(_Symbol, tick);
// tick.bid, tick.ask, tick.last, tick.volume, tick.time

Key Functions

Function	Purpose
CopyRates()	Bulk OHLCV data
CopyOpen/High/Low/Close()	Individual price arrays
CopyTime()	Bar open times
CopyBuffer()	Indicator buffer values
iBars()	Bar count for symbol/period
iBarShift()	Bar index by time
iTime()	Bar open time by shift
SymbolInfoTick()	Current tick data

5. Risk Management and Lot Sizing

Core Concept: PointValue

PointValue = profit/loss in profit-currency for a 1-point price move on 1 lot. This is the foundation for all risk calculations.

double PointValue(string symbol) {
    double point    = SymbolInfoDouble(symbol, SYMBOL_POINT);
    double contract = SymbolInfoDouble(symbol, SYMBOL_TRADE_CONTRACT_SIZE);
    ENUM_SYMBOL_CALC_MODE mode =
        (ENUM_SYMBOL_CALC_MODE)SymbolInfoInteger(symbol, SYMBOL_TRADE_CALC_MODE);

    switch (mode) {
        case SYMBOL_CALC_MODE_FOREX:
        case SYMBOL_CALC_MODE_FOREX_NO_LEVERAGE:
        case SYMBOL_CALC_MODE_CFD:
        case SYMBOL_CALC_MODE_CFDINDEX:
        case SYMBOL_CALC_MODE_CFDLEVERAGE:
        case SYMBOL_CALC_MODE_EXCH_STOCKS:
        case SYMBOL_CALC_MODE_EXCH_STOCKS_MOEX:
            return point * contract;

        case SYMBOL_CALC_MODE_FUTURES:
        case SYMBOL_CALC_MODE_EXCH_FUTURES:
        case SYMBOL_CALC_MODE_EXCH_FUTURES_FORTS:
            return point * SymbolInfoDouble(symbol, SYMBOL_TRADE_TICK_VALUE)
                                / SymbolInfoDouble(symbol, SYMBOL_TRADE_TICK_SIZE);
    }
    return 0;
}

Key distinction:

• SYMBOL_TRADE_TICK_VALUE = profit-currency per tick for 1 lot (broker-supplied)
• PointValue = profit-currency per 1 point for 1 lot (computed)
• loss = points × PointValue × Lots

Direction A: SL Distance Points → SL Price

Given a stop loss distance in points, compute the SL price level.

double CalcSLFromPoints(string symbol, double openPrice, int slPoints,
                        bool isBuy) {
    double point = SymbolInfoDouble(symbol, SYMBOL_POINT);
    double slDistPrice = slPoints * point;

    if (isBuy)
        return NormalizeDouble(openPrice - slDistPrice,
                              (int)SymbolInfoInteger(symbol, SYMBOL_DIGITS));
    else
        return NormalizeDouble(openPrice + slDistPrice,
                              (int)SymbolInfoInteger(symbol, SYMBOL_DIGITS));
}

Direction B: Risk % → SL Price (fixed lot size)

Given account balance, risk %, and lot size, compute where SL must be placed.

CRITICAL: When profit_currency ≠ account_currency, convert risk amount first.

double CalcSLFromRisk(string symbol, double balance, double riskPct,
                      double lots, double openPrice, bool isBuy) {
    double pv = PointValue(symbol);
    if (pv == 0 || lots == 0) return 0;

    double riskAmount = balance * riskPct / 100.0;

    // If profit currency differs from account currency, convert.
    // Example: USDJPY → profit=JPY, account=USD → multiply by USDJPY bid
    string profCy  = SymbolInfoString(symbol, SYMBOL_CURRENCY_PROFIT);
    string accCy   = AccountInfoString(ACCOUNT_CURRENCY);
    if (profCy != accCy) {
        // Find exchange rate pair: look for a Forex symbol with
        // base=accCy, profit=profCy (or reverse)
        string rateSym = "";
        int dir = FindFXRate(accCy, profCy, rateSym);
        if (dir == 0) { Print("Cannot convert ", profCy, "→", accCy); return 0; }
        MqlTick tick;
        SymbolInfoTick(rateSym, tick);
        double rate = (dir > 0) ? tick.bid : 1.0 / tick.ask;
        riskAmount *= rate;  // risk in profit currency
    }

    double points  = riskAmount / (pv * lots);
    double slPrice = points * SymbolInfoDouble(symbol, SYMBOL_POINT);

    if (isBuy)
        return NormalizeDouble(openPrice - slPrice,
                              (int)SymbolInfoInteger(symbol, SYMBOL_DIGITS));
    else
        return NormalizeDouble(openPrice + slPrice,
                              (int)SymbolInfoInteger(symbol, SYMBOL_DIGITS));
}

// Helper: find a Forex pair that converts from→to
// Returns +1 if pair is from/to, -1 if to/from, 0 if not found
int FindFXRate(string from, string to, string &result) {
    for (int i = 0; i < SymbolsTotal(true); i++) {
        string sym = SymbolName(i, true);
        ENUM_SYMBOL_CALC_MODE m =
            (ENUM_SYMBOL_CALC_MODE)SymbolInfoInteger(sym, SYMBOL_TRADE_CALC_MODE);
        if (m != SYMBOL_CALC_MODE_FOREX &&
            m != SYMBOL_CALC_MODE_FOREX_NO_LEVERAGE) continue;
        string base  = SymbolInfoString(sym, SYMBOL_CURRENCY_BASE);
        string profit = SymbolInfoString(sym, SYMBOL_CURRENCY_PROFIT);
        if (base == from && profit == to) { result = sym; return +1; }
        if (base == to   && profit == from) { result = sym; return -1; }
    }
    return 0;
}

Direction C: SL Price → Lot Size (risk-based sizing)

Given a fixed SL price, compute the lot size so loss matches the risk budget.

double CalcLotsFromSL(string symbol, double balance, double riskPct,
                      double openPrice, double slPrice) {
    double pv = PointValue(symbol);
    if (pv == 0) return 0;

    double riskAmount = balance * riskPct / 100.0;

    // Currency conversion (same as Direction B above)
    string profCy = SymbolInfoString(symbol, SYMBOL_CURRENCY_PROFIT);
    string accCy  = AccountInfoString(ACCOUNT_CURRENCY);
    if (profCy != accCy) {
        string rateSym = "";
        int dir = FindFXRate(accCy, profCy, rateSym);
        if (dir == 0) return 0;
        MqlTick tick;
        SymbolInfoTick(rateSym, tick);
        double rate = (dir > 0) ? tick.bid : 1.0 / tick.ask;
        riskAmount *= rate;
    }

    double slDistPrice = MathAbs(openPrice - slPrice);
    if (slDistPrice == 0) return 0;

    double point = SymbolInfoDouble(symbol, SYMBOL_POINT);
    double points = slDistPrice / point;
    double rawLots = riskAmount / (pv * points);

    // Normalize to broker constraints
    double minLot  = SymbolInfoDouble(symbol, SYMBOL_VOLUME_MIN);
    double maxLot  = SymbolInfoDouble(symbol, SYMBOL_VOLUME_MAX);
    double lotStep = SymbolInfoDouble(symbol, SYMBOL_VOLUME_STEP);

    double lot = MathFloor(rawLots / lotStep) * lotStep;
    lot = MathMax(lot, minLot);
    lot = MathMin(lot, maxLot);
    return NormalizeDouble(lot, 2);
}

Profit Verification

Use OrderCalcProfit (EA/scripts only) or manual formula to verify:

// Using OrderCalcProfit
double profit;
OrderCalcProfit(ORDER_TYPE_BUY, symbol, lots, openPrice, closePrice, profit);
// profit is in profit currency

// Manual formula (Forex/CFD)
double profit = (closePrice - openPrice) * ContractSize * Lots;

// Manual formula (Futures)
double profit = (closePrice - openPrice) * TickValue / TickSize * Lots;

Risk-to-Reward Ratio

// Minimum 1:2 RR
double slDistance = MathAbs(price - sl);
double tpDistance = slDistance * 2;  // 1:2 minimum
double tp = (orderType == ORDER_TYPE_BUY) ? price + tpDistance : price - tpDistance;

Position Sizing Rules

1. Never risk more than 1-2% per trade
2. Calculate SL price from risk% and lot size (Direction B), OR calculate lot size from SL price and risk% (Direction C)
3. Always verify with OrderCalcProfit or manual formula
4. Normalize SL with NormalizeDouble(price, SYMBOL_DIGITS)
5. Check SL distance ≥ SYMBOL_TRADE_STOPS_LEVEL × Point
6. Normalize lots to SYMBOL_VOLUME_STEP, clamp to [VOLUME_MIN, VOLUME_MAX]
7. When profit_currency ≠ account_currency, convert risk amount via FX rate

6. Backtesting and Optimization

Strategy Tester

The Strategy Tester is built into MT5. Key concepts:

1. Single Test: run EA once with fixed parameters
2. Optimization: genetic algorithm searches parameter space
3. Custom Criterion: OnTester() returns optimization value

Important: The Strategy Tester is GUI-only. metatester64.exe only manages remote testing agents (install/start/stop), not test execution itself. terminal64.exe has no command-line parameters. Backtesting and optimization must be performed through the MT5 Strategy Tester GUI.

CLI Automation — What Can and Cannot Be Automated

Task	CLI Possible?	How
Syntax check	✅	wine MetaEditor64.exe /compile:"path" /log /s
Compile .mq5 → .ex5	✅	wine MetaEditor64.exe /compile:"path" /log
Run backtest	❌	GUI only: Strategy Tester
Run optimization	❌	GUI only: Strategy Tester
Parse test report	✅	scripts/parse_tester_report.py

MetaEditor CLI syntax (Linux/Wine, from MT5 base directory):

wine MetaEditor64.exe /compile:"MQL5/Experts/MyEA.mq5" /log       # compile
wine MetaEditor64.exe /compile:"MQL5/Experts/MyEA.mq5" /log /s    # syntax check only

Log file: same directory as source, same name with .log extension.

OnTester Handler

double OnTester() {
    // Called after each test pass
    // Return value used as "Custom max" optimization criterion

    double profit   = TesterStatistics(STAT_PROFIT);
    double dd       = TesterStatistics(STAT_BALANCE_DDREL_PERCENT);
    double trades   = TesterStatistics(STAT_TRADES);
    double pf       = TesterStatistics(STAT_PROFIT_FACTOR);
    double sharpe   = TesterStatistics(STAT_SHARPE_RATIO);

    // Minimum trade count filter
    if (trades < 50) return 0;

    // Custom criterion: profit factor * (1 - max drawdown%)
    return pf * (1.0 - dd / 100.0);
}

Key Statistics

Stat	Description
STAT_PROFIT	Net profit/loss
STAT_PROFIT_FACTOR	Gross profit / gross loss
STAT_BALANCE_DDREL_PERCENT	Max balance drawdown %
STAT_SHARPE_RATIO	Sharpe ratio
STAT_TRADES	Number of trades
STAT_PROFIT_TRADES	Winning trades
STAT_LOSS_TRADES	Losing trades
STAT_EXPECTED_PAYOFF	Average profit per trade
STAT_RECOVERY_FACTOR	Profit / max drawdown

Parameter Optimization

When running optimization in the GUI, define parameter ranges as [start, stop, step] (stop inclusive). For example:

Parameter	Start	Stop	Step
RiskPercent	0.5	3.0	0.5
Slippage	5	20	5
MagicNumber	10000	10010	1

In MT5 Strategy Tester: set each input parameter to "Enable optimization", then configure range/step in the optimization tab.

Backtesting Workflow

1. Code the EA with OnTick(), OnInit(), OnDeinit()
2. Add OnTester() for custom optimization criterion
3. Compile and check syntax via CLI (see CLI Automation above)
4. In MT5: Strategy Tester → select EA → set symbol/timeframe/period
5. Choose "Open prices only" for speed, "Every tick" for accuracy
6. Run single test → check results
7. Run optimization → find best parameters
8. Validate with out-of-sample data

EA Development Cycle

Code → Syntax Check (CLI) → Compile (CLI)
  ↓
GUI: Single Test → Check Results
  ↓
If promising → GUI: Optimize → Analyze Report
  ↓
If validated → GUI: Forward Test → Deploy
  ↓
Monitor → Collect Data → Refine → Repeat

Note: steps marked (CLI) can be automated via mql5_helper.py or direct Wine commands. GUI steps require human interaction.

Report Analysis — Interpreting Tester Results

After each backtest, MT5 exports an HTML report. Use scripts/parse_tester_report.py to extract structured data, or read the HTML directly. Key areas to evaluate:

1. Data Quality Gate

Always check first. If history quality is poor, all metrics are suspect.

Metric	Acceptable	Action if Failed
History Quality	≥ 95% real ticks	Re-download tick data or use different broker
Bars	Enough for strategy (e.g. 1000+ for H4)	Extend test period
Modelling quality	Every tick or Every tick based on real ticks	Never trust "Open prices only" for final eval

2. Profitability Metrics

Metric	Good	Warning	Bad
Net Profit	> 0	≈ 0	< 0
Profit Factor	> 1.5	1.0–1.5	< 1.0
Expected Payoff	> 0	≈ 0	< 0
Recovery Factor	> 2.0	1.0–2.0	< 1.0

Profit Factor < 1.0 = guaranteed loss. The EA loses more than it wins. No amount of parameter tuning will fix a fundamentally negative PF — the strategy logic itself needs rethinking.

3. Drawdown Analysis

Drawdown is the real killer. A 100% drawdown means account wiped.

Metric	Safe	Risky	Dangerous
Max DD%	< 20%	20–50%	> 50%
DD Absolute / Deposit	< 0.5x	0.5–1x	> 1x (blown)

Check both Balance DD and Equity DD. Equity DD captures floating losses that haven't realized yet — often much worse than balance DD.

If Balance DD Max% ≈ 100%, the account was wiped. Look at the balance curve: did it recover or flatline at zero?

4. Trade Distribution

Metric	Healthy	Concerning
Win Rate	40–60%	< 30% or > 70%
Avg Win / Avg Loss	> 1.5	< 1.0
Profit Trades %	> 40%	< 30%
Largest Loss / Avg Loss	< 3x	> 5x (outlier risk)

Low win rate is fine if avg win >> avg loss (trend following). High win rate is fine if avg loss << avg win (mean reversion). Red flag: low win rate AND small avg win = guaranteed bleed.

5. Consecutive Losses

Metric	Tolerable	Stressed
Max Consecutive Losses	< 5	> 8
Max Consecutive Loss $	< 2x deposit	> deposit

More than 8 consecutive losses suggests the strategy has long anti-trend periods. With martingale or grid sizing, consecutive losses compound catastrophically.

6. Holding Time

Pattern	Meaning	Risk
Very short avg (< 1 min)	Scalping / arbitrage	Spread/slippage sensitive
Very long avg (> 100 hrs)	Swing / position trading	Gap/overnight risk
Huge variance (min vs max)	Mixed strategy	Hard to predict behavior

7. MFE/MAE Analysis

• MFE (Most Favorable Excursion): how far price went in your favor before exit. High MFE + low profit = premature exit (tight TP).
• MAE (Most Adverse Excursion): how far price went against you. High MAE + small loss = lucky exit (SL barely held).
• Correlation (Profits, MAE): high positive = losses come from large adverse moves (SL too loose or absent).
• Correlation (MFE, MAE): negative = when price moves far in one direction, it doesn't retrace (good for trend following).

8. Stop-Out Detection

Stop-outs (comment contains so) mean margin was insufficient — the broker force-closed before SL was reached. This is always a critical bug:

Root causes:
1. SL too far from entry → floating loss exceeds available margin
2. Lot size too large for account balance
3. Risk per trade exceeds account capacity
4. Multiple concurrent positions drain margin

Fix: reduce lot size, tighten SL, or reduce concurrent positions.

9. Short vs Long Bias

Compare Short Trades (won%) vs Long Trades (won%):

• Heavily skewed (e.g. 91 long / 5 short) → EA only trades one direction
• Check if this is intentional (bullish filter) or a bug
• In trending markets, one-direction bias can mask poor signal quality

10. Commission & Swap Impact

In the Deals table, check Commission and Swap columns:

• Commission should be consistent per deal (proportional to volume)
• Swap accumulates on overnight positions — can turn winners into losers
• Profit = Price P&L + Commission + Swap — verify this sums correctly

7. Event Handlers Reference

Handler	When Called	Use Case
OnInit()	EA/indicator starts	Initialize handles, variables
OnDeinit()	EA/indicator stops	Cleanup, release handles
OnTick()	New tick received	EA main logic
OnTimer()	Timer event	Periodic operations
OnTrade()	Trade event	React to trade changes
OnTradeTransaction()	Trade transaction	Detailed trade tracking
OnChartEvent()	Chart interaction	GUI buttons, objects
OnCalculate()	Indicator calculation	Indicator main logic
OnTester()	Test complete	Custom optimization criterion
OnTesterInit()	Optimization start	Setup for optimization
OnTesterPass()	Each optimization pass	Log intermediate results

8. Common Pitfalls

General

1. Always check ResultRetcode() after PositionOpen() — success != execution
2. Use SetExpertMagicNumber() to distinguish your EA's trades
3. Normalize prices with NormalizeDouble(price, SYMBOL_DIGITS)
4. Check Bars() > N before trading to ensure enough history
5. Use ArraySetAsSeries(true) for timeseries arrays (index 0 = latest)
6. Release indicator handles in OnDeinit() with IndicatorRelease()
7. Don't trade on OnInit() — wait for first OnTick()
8. Account type matters: Hedging requires iterating positions, Netting uses select
9. Spread varies: use SymbolInfoInteger(_Symbol, SYMBOL_SPREAD) for live spread
10. Timer in tester: use EventSetTimer() in OnInit(), not hardcoded delays

SL/TP and Risk Calculation

11. PointValue ≠ TICK_VALUE: SYMBOL_TRADE_TICK_VALUE is per tick (broker-defined step), PointValue = point × ContractSize is per point (smallest price unit). For most Forex: TickSize = Point, so they coincide; for futures/metals they may differ.
12. TickSize ≠ Point: Always use the correct formula for the symbol's SYMBOL_TRADE_CALC_MODE. Forex/CFD: loss = delta_price × ContractSize × Lots. Futures: loss = delta_price × TickValue / TickSize × Lots.
13. Profit currency ≠ Account currency: USDJPY profit is JPY, not USD. Risk amount must be converted: risk_JPY = risk_USD × USDJPY_bid. Failing this makes risk 100×+ too small.
14. NormalizeDouble introduces rounding: SL price rounded to SYMBOL_DIGITS causes ~0.01-0.02% deviation from target loss. Acceptable; verify with OrderCalcProfit.
15. Lot step quantization: MathFloor(rawLots / lotStep) * lotStep can leave residual risk unmet. For large lot_step or small risk budgets, actual loss may differ from target by up to one lot_step worth of loss.
16. STOPS_LEVEL check: SL must be ≥ SYMBOL_TRADE_STOPS_LEVEL × Point from current price. If stops_level ≤ 0, use a safety margin (e.g. 150 points).

9. Quick Reference — EA Skeleton

//+------------------------------------------------------------------+
//|                                            MyExpertAdvisor.mq5   |
//+------------------------------------------------------------------+
#property copyright "Your Name"
#property link      ""
#property version   "1.00"

#include <Trade\Trade.mqh>

input double RiskPercent   = 1.0;    // Risk % per trade
input int    Slippage      = 10;     // Max slippage in points
input int    MagicNumber   = 12345;  // EA magic number

#define EA_MAGIC MagicNumber

CTrade trade;
bool   IsHedging;
datetime lastBarTime = 0;

//+------------------------------------------------------------------+
//| PointValue: profit-currency per 1-point move for 1 lot            |
//+------------------------------------------------------------------+
double PointValue(string symbol) {
    double point    = SymbolInfoDouble(symbol, SYMBOL_POINT);
    double contract = SymbolInfoDouble(symbol, SYMBOL_TRADE_CONTRACT_SIZE);
    ENUM_SYMBOL_CALC_MODE mode =
        (ENUM_SYMBOL_CALC_MODE)SymbolInfoInteger(symbol, SYMBOL_TRADE_CALC_MODE);
    if (mode == SYMBOL_CALC_MODE_FUTURES ||
        mode == SYMBOL_CALC_MODE_EXCH_FUTURES ||
        mode == SYMBOL_CALC_MODE_EXCH_FUTURES_FORTS)
        return point * SymbolInfoDouble(symbol, SYMBOL_TRADE_TICK_VALUE)
                            / SymbolInfoDouble(symbol, SYMBOL_TRADE_TICK_SIZE);
    return point * contract;  // Forex, CFD, Stocks
}

//+------------------------------------------------------------------+
//| FindFXRate: locate a Forex pair for currency conversion            |
//+------------------------------------------------------------------+
int FindFXRate(string from, string to, string &result) {
    for (int i = 0; i < SymbolsTotal(true); i++) {
        string sym = SymbolName(i, true);
        ENUM_SYMBOL_CALC_MODE m =
            (ENUM_SYMBOL_CALC_MODE)SymbolInfoInteger(sym, SYMBOL_TRADE_CALC_MODE);
        if (m != SYMBOL_CALC_MODE_FOREX &&
            m != SYMBOL_CALC_MODE_FOREX_NO_LEVERAGE) continue;
        string base   = SymbolInfoString(sym, SYMBOL_CURRENCY_BASE);
        string profit = SymbolInfoString(sym, SYMBOL_CURRENCY_PROFIT);
        if (base == from && profit == to) { result = sym; return +1; }
        if (base == to   && profit == from) { result = sym; return -1; }
    }
    return 0;
}

//+------------------------------------------------------------------+
//| CalcSLFromRisk: risk% + lots → SL price                           |
//+------------------------------------------------------------------+
double CalcSLFromRisk(string symbol, double balance, double riskPct,
                      double lots, double openPrice, bool isBuy) {
    double pv = PointValue(symbol);
    if (pv == 0 || lots == 0) return 0;
    double riskAmount = balance * riskPct / 100.0;

    // Currency conversion if needed
    string profCy = SymbolInfoString(symbol, SYMBOL_CURRENCY_PROFIT);
    string accCy  = AccountInfoString(ACCOUNT_CURRENCY);
    if (profCy != accCy) {
        string rateSym = "";
        int dir = FindFXRate(accCy, profCy, rateSym);
        if (dir == 0) return 0;
        MqlTick tick; SymbolInfoTick(rateSym, tick);
        riskAmount *= (dir > 0) ? tick.bid : 1.0 / tick.ask;
    }

    double points  = riskAmount / (pv * lots);
    double slPrice = points * SymbolInfoDouble(symbol, SYMBOL_POINT);
    int digits = (int)SymbolInfoInteger(symbol, SYMBOL_DIGITS);
    return isBuy ? NormalizeDouble(openPrice - slPrice, digits)
                 : NormalizeDouble(openPrice + slPrice, digits);
}

//+------------------------------------------------------------------+
//| CalcLotsFromSL: SL price + risk% → lot size                       |
//+------------------------------------------------------------------+
double CalcLotsFromSL(string symbol, double balance, double riskPct,
                      double openPrice, double slPrice) {
    double pv = PointValue(symbol);
    if (pv == 0) return 0;
    double riskAmount = balance * riskPct / 100.0;

    string profCy = SymbolInfoString(symbol, SYMBOL_CURRENCY_PROFIT);
    string accCy  = AccountInfoString(ACCOUNT_CURRENCY);
    if (profCy != accCy) {
        string rateSym = "";
        int dir = FindFXRate(accCy, profCy, rateSym);
        if (dir == 0) return 0;
        MqlTick tick; SymbolInfoTick(rateSym, tick);
        riskAmount *= (dir > 0) ? tick.bid : 1.0 / tick.ask;
    }

    double slDist = MathAbs(openPrice - slPrice);
    if (slDist == 0) return 0;
    double points = slDist / SymbolInfoDouble(symbol, SYMBOL_POINT);
    double rawLots = riskAmount / (pv * points);

    double minLot  = SymbolInfoDouble(symbol, SYMBOL_VOLUME_MIN);
    double maxLot  = SymbolInfoDouble(symbol, SYMBOL_VOLUME_MAX);
    double lotStep = SymbolInfoDouble(symbol, SYMBOL_VOLUME_STEP);
    double lot = MathFloor(rawLots / lotStep) * lotStep;
    lot = MathMax(lot, minLot);
    lot = MathMin(lot, maxLot);
    return NormalizeDouble(lot, 2);
}

//+------------------------------------------------------------------+
int OnInit() {
    IsHedging = ((ENUM_ACCOUNT_MARGIN_MODE)
        AccountInfoInteger(ACCOUNT_MARGIN_MODE) == ACCOUNT_MARGIN_MODE_RETAIL_HEDGING);

    trade.SetExpertMagicNumber(EA_MAGIC);
    trade.SetMarginMode();
    trade.SetTypeFillingBySymbol(Symbol());
    trade.SetDeviationInPoints(Slippage);

    return INIT_SUCCEEDED;
}

//+------------------------------------------------------------------+
void OnDeinit(const int reason) {
    // Cleanup
}

//+------------------------------------------------------------------+
void OnTick() {
    // New bar check
    datetime barTime = iTime(_Symbol, _Period, 0);
    if (barTime == lastBarTime) return;
    lastBarTime = barTime;

    // Example: buy with 1% risk, SL at 500 points
    double bid = SymbolInfoDouble(_Symbol, SYMBOL_BID);
    int slPts = 500;
    double sl = CalcSLFromPoints(_Symbol, bid, slPts, true);
    // Or: double sl = CalcSLFromRisk(_Symbol,
    //         AccountInfoDouble(ACCOUNT_BALANCE), RiskPercent,
    //         0.10, bid, true);

    double lots = CalcLotsFromSL(_Symbol,
        AccountInfoDouble(ACCOUNT_BALANCE), RiskPercent, bid, sl);

    // Verify loss matches risk budget
    double profit;
    OrderCalcProfit(ORDER_TYPE_BUY, _Symbol, lots, bid, sl, profit);
    PrintFormat("SL=%.5f lots=%.2f expected_loss=%.2f",
                sl, lots, profit);

    // trade.Buy(lots, _Symbol, 0, sl, 0, "EA Signal");
}

//+------------------------------------------------------------------+
double OnTester() {
    double trades = TesterStatistics(STAT_TRADES);
    if (trades < 30) return 0;
    return TesterStatistics(STAT_PROFIT_FACTOR);
}

10. References

In this skill

• references/book/ — Programming book (learning path, 581 pages)
  • 00-intro/ — Introduction and IDE
  • 01-basis/ — Language fundamentals
  • 02-oop/ — Object-oriented programming
  • 03-common/ — Common functions (strings, files, math)
  • 04-applications/ — Charts, indicators, objects, events
  • 05-automation/ — Trading, symbols, tester
  • 06-advanced/ — Resources, SQLite, Python, OpenCL
• references/docs/ — API reference (4135 pages)
  • 19-trading/ — Trading functions (OrderSend, PositionGet, etc.)
  • 16-series/ — Timeseries access (CopyRates, CopyBuffer, etc.)
  • 26-indicators/ — Built-in indicators (iMA, iRSI, iMACD, etc.)
  • 24-customind/ — Custom indicator creation
  • 13-event-handlers/ — Event handlers (OnTick, OnTester, etc.)
  • 34-standardlibrary/ — Standard library (CTrade, CPositionInfo, etc.)
  • 01-constants/ — Enums and structures (MqlTradeRequest, ENUM_SYMBOL_CALC_MODE)
• references/symbol-spec/ — Symbol specification CSVs (broker-specific)
  • specs-XAUUSD.csv — XAUUSD: CFD Leverage, ContractSize=100, Digits=2
  • specs-USDJPY.csv — USDJPY: Forex, ContractSize=100000, Digits=3
• scripts/verify_sl_tp_formulas.py — Python verification of SL/TP risk formulas

External

• MQL5 Reference
• MQL5 Book
• Strategy Tester Guide