XAUUSD bots: the instrument details that break automated systems

The contract-size trap

Most brokers define one standard XAUUSD lot as 100 troy ounces. Some define it as 10. A few offer both, on different account types.

A bot that assumes 100 ounces on a broker using 10 will open positions a tenth of the intended size. Annoying, but survivable. A bot that assumes 10 on a broker using 100 opens positions ten times too large, and a single trade can take a quarter of the account.

The fix is straightforward and frequently skipped: read the contract size from the platform at runtime rather than hard-coding it. In MQL that is SymbolInfoDouble(symbol, SYMBOL_TRADE_CONTRACT_SIZE). Any gold EA that does not do this has an assumption baked into it that may not match your broker.

The pip ambiguity

Gold is quoted to two decimals. Whether a "pip" means 0.1 or 0.01 is a convention, not a standard, and both are in use.

At 0.1, a standard lot is $10 per pip and a typical daily range is 150–300 pips. At 0.01, the same lot is $1 per pip and the same range is 1,500–3,000 pips. A "150-pip stop" therefore means either 15.00 or 1.50 in price, which are entirely different trades.

Two practical rules. In signals and documentation, use price distance, "stop at 2331.00" cannot be misread. In code, derive from the symbol via point size and digits rather than assuming. MarketPro's gold signals always state absolute price levels for this reason.

Symbol naming and execution constraints

Gold appears under different names across brokers: XAUUSD, GOLD, XAUUSD.m, XAUUSDm, XAUUSD-ECN and others, often with a suffix identifying the account type. A bot with a hard-coded symbol string fails silently. No error, no trades, no obvious cause.

Three execution constraints also bite harder on gold than on currency pairs:

• Stop level. The minimum distance from current price at which a stop or limit may be placed. On gold this is often much wider than on forex, so a tight stop can be rejected outright.
• Freeze level. How close to price an order can be before it can no longer be modified. Which matters precisely when a bot most wants to move a stop.
• Rollover. A daily window where the spread widens sharply on every broker. A bot without a time filter enters into it and pays several times the normal cost.

What an automated system cannot do

Four limits are structural rather than a matter of build quality, and understanding them is most of what separates people who use automation well from people who lose money to it.

It cannot know what it has not been shown. A rule set encodes past relationships. When the regime changes (a trending market turns to chop, a correlation that held for two years breaks) the system keeps applying yesterday's logic with full confidence and no awareness that anything has changed.

Backtests overstate almost everything. A backtest with clean fills, fixed spread and no slippage is not a simulation of trading, it is a simulation of arithmetic. Add realistic spread, variable execution and the requeues that happen in fast markets, and a strategy that looked excellent frequently becomes marginal.

Optimisation finds coincidences. Tune enough parameters against enough history and you will find a setting that fits it perfectly. That setting describes the noise in that particular sample, not a property of the market, and it stops working the moment it meets data it was not fitted to. This is curve-fitting, and it is the single most common reason a purchased system fails.

Recovery logic hides risk instead of removing it. Martingale and grid systems produce beautiful equity curves for months, because doubling into a losing position converts many small losses into rare enormous ones. The curve is not evidence of an edge; it is evidence that the loss has not arrived yet.

The MarketPro Expert Advisor

MarketPro is building an Expert Advisor for MetaTrader 4 and MetaTrader 5. It is not available to download yet, and this page will say so until it is.

What is open today is the waiting list. Install the app, open the EA tab, and join it; everyone on the list is emailed when the builds go live. There is no charge and no card involved in joining.

When it does ship, three things will be true about it by design:

• You install and run it. It executes on your terminal, on your account, under your configuration. MarketPro never touches your account and exercises no discretion over your funds.
• It ships with a kill switch and an explicit as-is licence with no performance guarantee.
• Availability is limited by region. Distribution is restricted, and eligibility is determined by residence rather than by a checkbox on a page.

Meanwhile the thing that is live is the signal feed: vetted trade ideas with entry, stop and three targets that you place yourself. That is the manual equivalent of what the EA will automate, and it is available today with the free weekly signals.