Discussing the article: "Broker Reality Check (Part 1): Why Your EA Works on a Demo and Breaks on a Client's Broker"
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Check out the new article: Broker Reality Check (Part 1): Why Your EA Works on a Demo and Breaks on a Client's Broker.
Your Expert Advisor runs clean on your demo, then throws errors on a client's broker and quietly stops trading - and the code never changed. What changed is the broker's rulebook. This first article of the Broker Reality Check series builds a diagnostic EA that reads every relevant symbol trading condition - filling policy, stops and freeze levels, volume step, trade mode, swap and the triple-swap day - and flags the ones that silently break EAs, in plain language. It shows a green/amber/red panel, prints a report and dumps every Market Watch symbol to CSV, so you see why an OrderSend fails (10030, invalid stops, invalid volume) before it costs you a trade.
If you build EAs in MQL5, this has probably happened to you. You finish an Expert Advisor, it runs clean on your own account for weeks, you hand it to a client or move it to a different broker — and there it throws errors on every trade, or worse, it silently stops opening positions and you only notice days later. I have been there more than once. My first reaction used to be to dig through my own code hunting for the bug. Very often there is no bug: the code is fine. What changed is the broker. The log fills with return codes like 10030 (invalid order filling type), or rejections like invalid stops and invalid volume — and none of them are your logic.
Every broker imposes its own set of trading conditions on each symbol — the order filling policy it accepts, how far your stop-loss must sit from the price, the lot step it demands, whether it even lets you open both directions. Your terminal knows all of them, but they stay invisible until an OrderSend quietly fails against one. The Strategy Tester never warns you either, because it trades against your own broker's specs — the same ones your EA was written for. Move to another broker and the ground shifts under your feet.
In this article, the first of a series I'm calling Broker Reality Check, I build a small diagnostic EA that reads those conditions for you and flags the ones that break EAs, in plain language, before they cost you a trade. It is a tool, not a strategy. Later parts will measure the cost side of the broker (swap, spread); this one maps the rulebook.
Author: Walter Marcelo Rando