Trading
Orders placed for a member against a market, the trades they produce, and cancellation.
An order takes member_id, market, side and ord_type, plus whichever of
price, volume and amount the order type needs. client_order_id is a
string and doubles as a lookup key on the order list — which is the way to
check whether an order was created before sending it again.
Working out which asset moves
An order names only market_id and side; there are no separate fields for the
asset bought and the asset sold. Derive them from the market and the side: on
btcusdt a buy receives BTC and pays USDT, a sell does the reverse.
Order size
Markets have a minimum order size, and it is enforced when the order is placed rather than published in the market object. Handle the refusal in your flow instead of validating size up front.