Contract specifications that differ between brokers for the same symbol

[Amanhasnoname]

Two brokers may both list EUR/USD, and the contract details differ. Standard lot size is usually 100,000, but some brokers define a lot differently. Minimum lot, lot step, tick size, and margin requirement vary too.

For automated systems, the assumptions can break when moving to a new broker. A position-size calculation built on one set of specs produces the wrong size on another. A 0.01 lot minimum on one platform may be 0.1 on another.

Margin requirements differ by symbol and account type. A strategy that uses a certain share of margin on one broker might use double on another.

Commission structures reference the lot size, so a different contract size changes the effective cost per unit of exposure.

Before running on a new account, review the symbol specification page and compare against the previous one. Check lot step, tick value, stops level, freeze level, and swap rates.

Writing the specs into a configuration file and verifying them at startup prevents silent sizing errors.

Which contract spec difference has caught a strategy by surprise?