Build Order

Build an order payload without submitting it to the exchange. Returns the exchange-native signed order or request body for inspection, forwarding through a middleware layer, or deferred submission via submitOrder().

POST /api/{exchange}/buildOrder

Python

Polymarket

import pmxt

# Runs locally — never proxied through PMXT servers
exchange = pmxt.Polymarket(
    api_key="YOUR_API_KEY",
    api_secret="YOUR_API_SECRET",
    passphrase="YOUR_PASSPHRASE",
    private_key="YOUR_PRIVATE_KEY",
    proxy_address="YOUR_PROXY_ADDRESS",
    signature_type="gnosis-safe",
)
result = exchange.build_order(
    market_id="12345",
    outcome_id="67890",
    side="buy",
    type="market",
    amount=10,
    price=0.55,
    fee=1,
    tick_size=1,
    neg_risk=True,
    on_behalf_of=1,
)

200

{
  "success": true,
  "error": {
    "message": "<string>"
  },
  "data": {
    "exchange": "<string>",
    "params": {
      "marketId": "<string>",
      "outcomeId": "<string>",
      "amount": 123,
      "price": 123,
      "fee": 123,
      "tickSize": 123,
      "negRisk": true,
      "onBehalfOf": 123
    },
    "raw": "<unknown>",
    "signedOrder": {},
    "tx": {
      "to": "<string>",
      "data": "<string>",
      "value": "<string>",
      "chainId": 123
    }
  }
}

Path Parameters

exchange · enum<string> · required

The prediction market exchange to target.

Available options: polymarket, kalshi, kalshi-demo, opinion, smarkets, polymarket_us

Body

application/json

args · object[] · required

Required array length: 1 element

Show child attributes

credentials · object

Optional authentication credentials for exchange operations.

Show child attributes

Response

200 - application/json

Build Order response

success · boolean

Example:

true

error · object

Show child attributes

data · object

Show child attributes