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POST
/
api
/
users
/
{userId}
/
orders
Place Order
curl --request POST \
  --url https://trade.predexon.com/api/users/{userId}/orders \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <api-key>' \
  --data '
{
  "venue": "polymarket",
  "side": "buy",
  "amount": "<string>",
  "tokenId": "<string>",
  "ticker": "<string>",
  "outcome": "Yes",
  "price": "<string>",
  "type": "limit"
}
'
{
  "orderId": "kalshi-order-12345",
  "venue": "kalshi",
  "ticker": "KXBTC-25JAN10-B100000",
  "side": "buy",
  "outcome": "Yes",
  "amount": "25.00",
  "price": "0.55",
  "status": "filled",
  "createdAt": "2024-01-15T10:30:00.000Z"
}

​
Endpoint

POST /api/users/{userId}/orders
Place orders on Kalshi by setting venue: "kalshi" in the request body.
Kalshi trading requires USDC on Solana and SOL in your wallet. SOL is needed for Solana transaction fees.

​
Request Body

FieldTypeRequiredDescription
venuestringYesMust be "kalshi"
tickerstringYesMarket ticker from Kalshi List Markets
outcomestringYes"Yes" or "No" (case-sensitive)
sidestringYes"buy" or "sell"
amountstringYesUSDC to spend (buy) or shares to sell (sell)

​
Constraints

ConstraintValue
Min order> 1 USDC
Outcome valuesYes or No (case-sensitive)
Amount precision2 decimal places

​
Amount Semantics

SideAmount Represents
buyUSDC to spend
sellShares to sell
Kalshi orders execute atomically via DFlow - they either fill completely or fail. There’s no partial fill or orderbook. The price in the response is the execution price.
{
  "orderId": "kalshi-order-12345",
  "venue": "kalshi",
  "ticker": "KXBTC-25JAN10-B100000",
  "side": "buy",
  "outcome": "Yes",
  "amount": "25.00",
  "price": "0.55",
  "status": "filled",
  "createdAt": "2024-01-15T10:30:00.000Z"
}

Authorizations

​
x-api-key
string
header
required

Path Parameters

​
userId
string
required

Unique identifier for the user

Body

application/json
​
venue
enum<string>
required

Trading venue: polymarket or kalshi

Available options:
polymarket,
kalshi
​
side
enum<string>
required

Buy or sell

Available options:
buy,
sell
​
amount
string
required

USDC to spend (buy) or shares to sell (sell)

​
tokenId
string

Polymarket token ID (required for Polymarket orders)

​
ticker
string

Kalshi market ticker (required for Kalshi orders)

​
outcome
enum<string>

Yes or No (required for Kalshi, case-sensitive)

Available options:
Yes,
No
​
price
string

Price per share (0-1). Required for Polymarket limit orders. Must match tick size.

​
type
enum<string>

Order type (Polymarket only, defaults to limit)

Available options:
limit,
market

Response

201 - application/json

Order placed successfully

​
orderId
string

Unique order identifier

​
venue
string

Trading venue: polymarket or kalshi

​
tokenId
string

Polymarket token ID (Polymarket orders only)

​
ticker
string

Kalshi market ticker (Kalshi orders only)

​
side
string

Order side: buy or sell

​
outcome
string

The outcome being traded (e.g., Yes, No)

​
amount
string

Order amount in USDC

​
price
string

Order price (0-1)

​
status
string

Order status: live, matched, or filled

​
createdAt
string

ISO 8601 timestamp