context-trade-place-order

name	context-trade-place-order
description	Place a single limit or market order on a prediction market

Place Order

Buy or sell outcome shares on a prediction market with a limit or market order.

When to Use

The user wants to buy or sell YES or NO shares on a specific market.

Steps

1. Get current prices — call context_get_quotes (MCP) or ctx.markets.quotes(marketId) to see bid/ask/last.
2. Simulate the trade — call context_simulate_trade (MCP) or ctx.markets.simulate(marketId, { side, amount, amountType: "usd" }) to preview fill price, cost, and slippage.
3. Place the order:
   • MCP: context_place_order({ marketId, outcome: "yes", side: "buy", size: 10, price: 45 }) — omit price for a market order
   • SDK limit: ctx.orders.create({ marketId, outcome: "yes", side: "buy", priceCents: 45, size: 10 })
   • SDK market: ctx.orders.createMarket({ marketId, outcome: "yes", side: "buy", maxPriceCents: 99, maxSize: 10 })
   • CLI: context orders create --market <id> --outcome yes --side buy --price 45 --size 10
4. Verify — call context_my_orders or ctx.orders.mine(marketId) to confirm the order is open.

Gotchas

• Account must be set up and funded first. Check with context_account_setup or ctx.account.status(). If not ready, run setup and deposit before placing orders.
• Price must be 1–99 cents. 0 and 100 are invalid. Price represents the implied probability.
• Simulation doesn't guarantee fill price. The orderbook can change between simulate and place. Simulation is a preview, not a reservation.
• Market orders use different params — maxPriceCents and maxSize, not priceCents and size. This caps your worst-case fill price.
• NEVER set makerRoleConstraint: 1 (MAKER_ONLY). This causes InvalidRoleConstraint reverts that block the entire market. Always use the default (0 = ANY).
• Check the spread first. If the bid-ask spread is wide (>10 cents), a limit order at mid-price may sit unfilled. Consider adjusting toward the opposite side.

Verification

• Call context_my_orders or ctx.orders.mine(marketId) — your order should appear with status "open".
• If placing a market order, check the returned order object — status, percentFilled, and remainingSize should reflect immediate execution.

See Also

• Orders API — Full type definitions and method signatures
• EIP-712 Signing — How orders are signed (SDK handles automatically)