Expert Advisor: The Curve You Cannot Check
An expert advisor is a program that runs inside a trading platform, watches the market and places orders without a person present. Two very different objects share the name: one you wrote yourself, and one you bought with an equity curve nobody outside the seller can verify.
How it works
An expert advisor is a program that trades the account for you. It sits inside the trading platform, reads price as it arrives, and sends orders under rules written down in advance.
The term comes from one platform and stuck. MetaTrader called its automation scripts expert advisors; elsewhere the same object is a trading bot or plain automated trading.
Writing one is worth doing even if it never trades live. Code will not accept a vague rule, so every ambiguity that survived in a discretionary method becomes an exact condition or is dropped.
The one you wrote and the one you bought
A bought program arrives with a curve you cannot check. The code is usually compiled and unreadable, the test behind the curve is not reproducible, and the account is a screenshot. Some sellers are honest; the curve cannot tell you which.
Most sold ones survive by adding to losers. A program that doubles its position after each loss, a martingale or a grid, produces a beautiful curve for months and then returns the whole account in one afternoon. The smooth curve is the warning, not the evidence.
It has to run somewhere, and your laptop is not that place. A machine that sleeps, restarts for an update or drops its connection leaves an open position with nobody watching. A small hosted server is the practical answer.
In practice
An unwatched program fails quietly and keeps trading. A broken feed, a rejected order or a renamed symbol will not announce itself, so somebody must read the account daily.
It pays the spread on every order it ever sends. A rule that trades often can be right about direction and still finish behind, so cost belongs inside the backtesting.
And it will keep trading when nobody else is. Thin volume hours widen the spread and thin the book, and a program with no clock takes those fills happily.
Months of live results beat any backtest. Forward testing on a demonstration account is slow and boring, and it is the only stage that shows the program meeting real spreads and real gaps.
A weekend gap is where the martingale ends. An opening gap prices straight through the level the program was waiting for, and in forex it lands while the platform is shut.
So a hard stop in the code is not optional. The stop loss belongs at the broker, not only in the program’s memory: if the program dies, its intentions die with it.
Every round trip costs 2% of a bar. Entry and exit together consume about two per cent of a median bar’s range here, which is small per trade and not small across hundreds of them.
Checking one you did not write
Ask for a long live record on a real account, not a backtest. A strategy tester result describes the past, and a setting tuned until that past looks perfect is overfitting with a sales page attached.
Then look for one behaviour in particular: does it hold a loser and add to it? If positions grow while price moves against them, the curve you were shown has not met the day that ends it.
Measure the worst drawdown against the account you would actually fund. A fall that looks survivable on a large test balance can close a small live one, especially with leverage multiplying the same move.
Then run it small and live for months. There is no shortcut around that, and a seller who tells you the demonstration period is unnecessary has told you what you needed to know.
What an expert advisor is not
- It is not a source of trading signals. Signals are suggestions to a person; this places the order itself.
- It is not a strategy. It is the enforcement of one, and it cannot improve a rule that was never good.
- It is not institutional algo trading. That is execution at scale; this is one retail account and one script.
- It is not proof of anything. An equity curve is a claim, made by the party who wants to sell it.
When it fails
In a range the grid sellers look like geniuses. A program that fades every move is paid for doing so while price oscillates, and the account curve climbs in a straight, convincing line.
- When the range ends. The same program meets a trading range breakout holding its largest position of the run.
- When the connection drops. A position opened by a program that is no longer running has nobody managing it and no exit but the broker’s.
- When the parameters were fitted. Settings tuned to one particular stretch of history degrade from the first live bar onwards.
- When leverage rescales the drawdown. A fall the test survived at one position size closes the account at another.
- When the broker changes something. A widened spread, a renamed symbol or a new minimum stop distance can stop the code without stopping the trading.
- When you intervene halfway. Closing one of its trades by hand leaves the program managing a position it no longer understands.
The original data
The counts come from research/broker-coverage.json, a scan of the 31,760 videos in
research/search-study-corpus.jsonl. “Expert advisor” appears in 9 titles from 5 channels, median
11,637 views, maximum 323,870.
The generic names are far more crowded. “Trading bot” has 109 titles from 77 channels, median 9,739 and maximum 1,097,422; “automated trading” 43 titles, median 11,143; “algorithmic trading” 97 titles, median 5,184.
Two of them barely exist. “Strategy tester” has 9 titles from 4 channels at a median of 52,868 views, “overfitting” has 2 at a median of 299, and “risk of ruin” has none.
The price figures come from research/series-measurements.json, produced by
site/measure_series.py. On the shared 576-bar history a round trip costs 0.0098 price units, 45%
of the smallest bar, and 95% of bars sit below a prior peak, the longest such stretch 73 bars.
The absence is the finding. Across 31,760 titles, “trading bot” and “automated trading” together account for well over a hundred videos, and “risk of ruin” appears zero times.
The published conversation describes what the program does, never the probability that it empties the account. That silence is the number a martingale or grid program needs you not to ask for. Write down the longest losing streak yours can survive at your account size, and do not fund it until the seller states that number too.
Related
Trading bot is the same object under the name most of the internet uses. Strategy tester is the tool that produced the curve you are being asked to believe. Algo trading is the wider field this sits at the retail end of.
I have been sent a lot of these over the years, and the picture attached is always the same: a curve that climbs and barely dips. What I have never once been sent is the trade history behind it, which is the only part that would tell me anything. The ones I ran myself were valuable mostly for what writing them taught me about my own rules. If somebody will not show you the losing weeks, they are not hiding a secret, they are hiding the losing weeks.
— Michael Whitman
This page is educational, not financial advice. Test every idea on your own charts before risking money.