Minimum size is part of the usable price

An order book can show a clean best ask, but the trade you planned may still not fit. Minimum order size and tick size are part of the market's usable price, not footnotes to read later.

Price tells you where the market is quoting. Constraints tell you whether your order can exist at that quote.

Record the constraints with the quote

Save the outcome identifier, best bid, best ask, minimum order size, tick size, timestamp, and book hash together. A price without those fields is difficult to replay and easy to misread.

Keep the quote tied to the outcome you can actually trade. A nearby outcome or a different token can have a different book and different limits.

Test the intended size

Compare your planned quantity with the minimum order size before calling the setup actionable. If the size is larger, walk through the available levels instead of assuming the top line can absorb it.

Round the price to the allowed tick size and recalculate the expected fill. A one-tick change can matter when the original margin was small.

Recheck the same snapshot

Refresh the book before submitting and compare its hash with the snapshot used in your worksheet. If the hash changed, rebuild the fill estimate rather than carrying the old ladder forward.

The useful comparison is between the order you can submit and the price you can receive, not between a headline quote and an imaginary size.

Separate theoretical from executable

Keep a theoretical probability or midpoint estimate separate from the executable path. Add spread, fees, minimum size, tick rounding, and the capital that may remain locked.

The useful question is not whether a quote looks cheap. It is whether the market's rules let your intended size reach that quote with the assumptions you wrote down.

Further reading: Prices and order books · Order lifecycle · Current fees.

Explore the markets: Open Polymarket (referral link).