How to Build a MetaTrader 5 Robot with ChatGPT

The landscape of algorithmic trading has shifted. You no longer need to be a C++ expert to build a sophisticated Expert Advisor (EA) for MetaTrader 5 (MT5). With advent of large language models like ChatGPT, you can bridge gap between a trading idea and a functional MQL5 script in minutes.

However, ChatGPT is a co-pilot,  To create a robot that actually works without crashing your terminal, you need a structured approach.

Step 1: Define Your Strategy Architecture

Before opening ChatGPT, you must define your logic with mathematical precision. LLMs struggle with vague instructions like buy when it looks good.

A robust prompt should include:

• Indicators: (e.g., 50-period EMA and 200-period EMA).

• Entry Rules: (e.g., Buy when 50 EMA crosses above 200 EMA).

• Exit Rules: (e.g., Close when the opposite cross occurs or at a fixed Take Profit).

• Risk Management: (e.g., 1% risk per trade, fixed Stop Loss of 20 pips).

• Timeframes: (e.g., H1 chart).

Step 2: Prompting ChatGPT for MQL5 Code

The quality of your robot depends entirely on your prompt. Use a Role-Based prompting strategy.

Copy-Paste Template:

“Act as an expert MQL5 programmer. Write a fully functional Expert Advisor for MT5.

Strategy: Moving Average Crossover.

Rules: Buy when Fast MA (14) crosses above Slow MA (50). Sell when Fast MA crosses below Slow MA.

Inputs: Include external inputs for MA periods, Lot size (0.1), Stop Loss (50 points), and Take Profit (100 points).

Format: Use the standard OnInit(), OnDeinit(), and OnTick() structure. Ensure you use the CTrade class for execution.”

Step 3: Implementing the Code in MetaEditor

1. Open MetaEditor: In MT5, press F4 or click the “IDE” icon.

2. Create New File: Click New -> Expert Advisor (template) -> Name your bot.

3. Paste & Replace: Delete default template code and paste code from ChatGPT.

4. Compile: Press F7.

   • Green Check: Your bot is ready.

   • Red Errors: Copy error message from “Errors” tab at bottom, paste it back into ChatGPT, and ask: “I got this error in MetaEditor, please fix the code.”

Step 4: Backtesting and Optimization

Never run an AI-generated bot on a live account immediately. ChatGPT can sometimes hallucinate functions or use outdated syntax.

1. Strategy Tester: Press Ctrl + R in MT5.

2. Settings: Select your new EA, a currency pair (e.g., EURUSD), and a timeframe.

3. Run Simulation: Look forEquity Curve. If curve goes straight down, your logic or AI’s implementation of it needs refinement.

Common Pitfalls to Avoid

Pitfall	Why it Happens	Solution
Outdated Syntax	ChatGPT was trained on data that may predate recent MT5 updates.	Ask ChatGPT to use the Trade.mqh standard library.
Logic Loops	The bot might open 100 trades at once.	Ensure your prompt specifies “Only one trade open at a time.”
Hardcoded Values	Variables that can’t be changed without recoding.	Always ask for “Input Parameters” so you can adjust settings in the MT5 UI.