Place a paper order

curl --request POST \
  --url https://arena-predictions.com/api/v1/portfolio/orders \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "action": "buy",
  "type": "limit",
  "instrumentId": "ins_0123456789AB",
  "side": "yes",
  "count": 10,
  "limitPriceCents": 40,
  "timeInForce": "gtc",
  "idempotencyKey": "1b4e28ba-2fa1-41d2-883f-0016d3cca427"
}
'

import requests

url = "https://arena-predictions.com/api/v1/portfolio/orders"

payload = {
    "action": "buy",
    "type": "limit",
    "instrumentId": "ins_0123456789AB",
    "side": "yes",
    "count": 10,
    "limitPriceCents": 40,
    "timeInForce": "gtc",
    "idempotencyKey": "1b4e28ba-2fa1-41d2-883f-0016d3cca427"
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    action: 'buy',
    type: 'limit',
    instrumentId: 'ins_0123456789AB',
    side: 'yes',
    count: 10,
    limitPriceCents: 40,
    timeInForce: 'gtc',
    idempotencyKey: '1b4e28ba-2fa1-41d2-883f-0016d3cca427'
  })
};

fetch('https://arena-predictions.com/api/v1/portfolio/orders', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

{
  "status": "executed",
  "action": "buy",
  "type": "market",
  "idempotencyKey": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "replayed": true,
  "originalCreatedAt": "2023-11-07T05:31:56Z",
  "order": {
    "orderId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "action": "buy",
    "instrumentId": "<string>",
    "instrumentLabel": "<string>",
    "instrumentSide": "yes",
    "orderSide": "yes",
    "contracts": 123,
    "filledContracts": 123,
    "remainingContracts": 123,
    "limitCents": 123,
    "holdDollars": 123,
    "timeInForce": "<string>",
    "expiresAt": "2023-11-07T05:31:56Z",
    "status": "<string>",
    "createdAt": "2023-11-07T05:31:56Z",
    "type": "limit",
    "cancelReason": "<string>",
    "tradeId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "statedProbPct": 123,
    "placedVia": "<string>",
    "placedPrivate": true,
    "marketTicker": "<string>",
    "fillPriceCents": 123
  },
  "trade": {
    "tradeId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "instrumentId": "<string>",
    "instrumentLabel": "<string>",
    "instrumentSide": "yes",
    "boughtSide": "yes",
    "contracts": 123,
    "costDollars": 123,
    "statedProbPct": 123,
    "placedVia": "<string>",
    "placedPrivate": true,
    "parlayId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "fillVenue": "<string>",
    "openedAt": "2023-11-07T05:31:56Z",
    "status": "open",
    "closedAt": "2023-11-07T05:31:56Z",
    "closeReason": "<string>",
    "pnlDollars": 123,
    "resolvedOutcome": "yes",
    "marketTicker": "<string>",
    "entryCents": 123
  },
  "fillVenue": "kalshi",
  "mode": "paper",
  "venueData": true,
  "fillPriceCents": 123
}

{
  "status": "executed",
  "action": "buy",
  "type": "market",
  "idempotencyKey": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "replayed": true,
  "originalCreatedAt": "2023-11-07T05:31:56Z",
  "order": {
    "orderId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "action": "buy",
    "instrumentId": "<string>",
    "instrumentLabel": "<string>",
    "instrumentSide": "yes",
    "orderSide": "yes",
    "contracts": 123,
    "filledContracts": 123,
    "remainingContracts": 123,
    "limitCents": 123,
    "holdDollars": 123,
    "timeInForce": "<string>",
    "expiresAt": "2023-11-07T05:31:56Z",
    "status": "<string>",
    "createdAt": "2023-11-07T05:31:56Z",
    "type": "limit",
    "cancelReason": "<string>",
    "tradeId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "statedProbPct": 123,
    "placedVia": "<string>",
    "placedPrivate": true,
    "marketTicker": "<string>",
    "fillPriceCents": 123
  },
  "trade": {
    "tradeId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "instrumentId": "<string>",
    "instrumentLabel": "<string>",
    "instrumentSide": "yes",
    "boughtSide": "yes",
    "contracts": 123,
    "costDollars": 123,
    "statedProbPct": 123,
    "placedVia": "<string>",
    "placedPrivate": true,
    "parlayId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "fillVenue": "<string>",
    "openedAt": "2023-11-07T05:31:56Z",
    "status": "open",
    "closedAt": "2023-11-07T05:31:56Z",
    "closeReason": "<string>",
    "pnlDollars": 123,
    "resolvedOutcome": "yes",
    "marketTicker": "<string>",
    "entryCents": 123
  },
  "fillVenue": "kalshi",
  "mode": "paper",
  "venueData": true,
  "fillPriceCents": 123
}

{
  "error": {
    "code": "invalid_request",
    "message": "<string>",
    "retryAfterSeconds": 2
  }
}

{
  "error": {
    "code": "invalid_request",
    "message": "<string>",
    "retryAfterSeconds": 2
  }
}

{
  "error": {
    "code": "invalid_request",
    "message": "<string>",
    "retryAfterSeconds": 2
  }
}

{
  "error": {
    "code": "invalid_request",
    "message": "<string>",
    "retryAfterSeconds": 2
  }
}

{
  "error": {
    "code": "invalid_request",
    "message": "<string>",
    "retryAfterSeconds": 2
  }
}

{
  "error": {
    "code": "invalid_request",
    "message": "<string>",
    "retryAfterSeconds": 2
  }
}

{
  "error": {
    "code": "invalid_request",
    "message": "<string>",
    "retryAfterSeconds": 2
  }
}

{
  "error": {
    "code": "invalid_request",
    "message": "<string>",
    "retryAfterSeconds": 2
  }
}

Trading

Place a paper order

Places a paper order for the key owner, as the CLI and the MCP server do. Kalshi’s path; paper only, so nothing is sent to Kalshi or any venue. A market order fills now at the live price or is refused. A limit order fills at limitPriceCents or better, rests until it fills, is canceled or expires (gtc), or is canceled at once when it does not fill (ioc, fok). Opening a position needs Arena Basic. Every order counts against the hard trade limits (per key 10 new orders a minute and 50 a day, 20 sells and cancels a minute; per account 20, 100 and 40), which are always enforced. No ticker, title or price in the answer while the venue-data switch is off.

POST

portfolio

orders

Place a paper order

curl --request POST \
  --url https://arena-predictions.com/api/v1/portfolio/orders \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "action": "buy",
  "type": "limit",
  "instrumentId": "ins_0123456789AB",
  "side": "yes",
  "count": 10,
  "limitPriceCents": 40,
  "timeInForce": "gtc",
  "idempotencyKey": "1b4e28ba-2fa1-41d2-883f-0016d3cca427"
}
'

import requests

url = "https://arena-predictions.com/api/v1/portfolio/orders"

payload = {
    "action": "buy",
    "type": "limit",
    "instrumentId": "ins_0123456789AB",
    "side": "yes",
    "count": 10,
    "limitPriceCents": 40,
    "timeInForce": "gtc",
    "idempotencyKey": "1b4e28ba-2fa1-41d2-883f-0016d3cca427"
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    action: 'buy',
    type: 'limit',
    instrumentId: 'ins_0123456789AB',
    side: 'yes',
    count: 10,
    limitPriceCents: 40,
    timeInForce: 'gtc',
    idempotencyKey: '1b4e28ba-2fa1-41d2-883f-0016d3cca427'
  })
};

fetch('https://arena-predictions.com/api/v1/portfolio/orders', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

{
  "status": "executed",
  "action": "buy",
  "type": "market",
  "idempotencyKey": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "replayed": true,
  "originalCreatedAt": "2023-11-07T05:31:56Z",
  "order": {
    "orderId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "action": "buy",
    "instrumentId": "<string>",
    "instrumentLabel": "<string>",
    "instrumentSide": "yes",
    "orderSide": "yes",
    "contracts": 123,
    "filledContracts": 123,
    "remainingContracts": 123,
    "limitCents": 123,
    "holdDollars": 123,
    "timeInForce": "<string>",
    "expiresAt": "2023-11-07T05:31:56Z",
    "status": "<string>",
    "createdAt": "2023-11-07T05:31:56Z",
    "type": "limit",
    "cancelReason": "<string>",
    "tradeId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "statedProbPct": 123,
    "placedVia": "<string>",
    "placedPrivate": true,
    "marketTicker": "<string>",
    "fillPriceCents": 123
  },
  "trade": {
    "tradeId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "instrumentId": "<string>",
    "instrumentLabel": "<string>",
    "instrumentSide": "yes",
    "boughtSide": "yes",
    "contracts": 123,
    "costDollars": 123,
    "statedProbPct": 123,
    "placedVia": "<string>",
    "placedPrivate": true,
    "parlayId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "fillVenue": "<string>",
    "openedAt": "2023-11-07T05:31:56Z",
    "status": "open",
    "closedAt": "2023-11-07T05:31:56Z",
    "closeReason": "<string>",
    "pnlDollars": 123,
    "resolvedOutcome": "yes",
    "marketTicker": "<string>",
    "entryCents": 123
  },
  "fillVenue": "kalshi",
  "mode": "paper",
  "venueData": true,
  "fillPriceCents": 123
}

{
  "status": "executed",
  "action": "buy",
  "type": "market",
  "idempotencyKey": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "replayed": true,
  "originalCreatedAt": "2023-11-07T05:31:56Z",
  "order": {
    "orderId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "action": "buy",
    "instrumentId": "<string>",
    "instrumentLabel": "<string>",
    "instrumentSide": "yes",
    "orderSide": "yes",
    "contracts": 123,
    "filledContracts": 123,
    "remainingContracts": 123,
    "limitCents": 123,
    "holdDollars": 123,
    "timeInForce": "<string>",
    "expiresAt": "2023-11-07T05:31:56Z",
    "status": "<string>",
    "createdAt": "2023-11-07T05:31:56Z",
    "type": "limit",
    "cancelReason": "<string>",
    "tradeId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "statedProbPct": 123,
    "placedVia": "<string>",
    "placedPrivate": true,
    "marketTicker": "<string>",
    "fillPriceCents": 123
  },
  "trade": {
    "tradeId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "instrumentId": "<string>",
    "instrumentLabel": "<string>",
    "instrumentSide": "yes",
    "boughtSide": "yes",
    "contracts": 123,
    "costDollars": 123,
    "statedProbPct": 123,
    "placedVia": "<string>",
    "placedPrivate": true,
    "parlayId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "fillVenue": "<string>",
    "openedAt": "2023-11-07T05:31:56Z",
    "status": "open",
    "closedAt": "2023-11-07T05:31:56Z",
    "closeReason": "<string>",
    "pnlDollars": 123,
    "resolvedOutcome": "yes",
    "marketTicker": "<string>",
    "entryCents": 123
  },
  "fillVenue": "kalshi",
  "mode": "paper",
  "venueData": true,
  "fillPriceCents": 123
}

{
  "error": {
    "code": "invalid_request",
    "message": "<string>",
    "retryAfterSeconds": 2
  }
}

{
  "error": {
    "code": "invalid_request",
    "message": "<string>",
    "retryAfterSeconds": 2
  }
}

{
  "error": {
    "code": "invalid_request",
    "message": "<string>",
    "retryAfterSeconds": 2
  }
}

{
  "error": {
    "code": "invalid_request",
    "message": "<string>",
    "retryAfterSeconds": 2
  }
}

{
  "error": {
    "code": "invalid_request",
    "message": "<string>",
    "retryAfterSeconds": 2
  }
}

{
  "error": {
    "code": "invalid_request",
    "message": "<string>",
    "retryAfterSeconds": 2
  }
}

{
  "error": {
    "code": "invalid_request",
    "message": "<string>",
    "retryAfterSeconds": 2
  }
}

{
  "error": {
    "code": "invalid_request",
    "message": "<string>",
    "retryAfterSeconds": 2
  }
}

Authorizations

Authorization

string

header

required

Authorization: Bearer arena_sk_... (the x-arena-key header is accepted too). Keys are made in Settings (https://arena-predictions.com/settings#api-keys) or with arena keys create, shown once, stored hashed.

Body

application/json

A buy names instrumentId or ticker, side and count. A sell names tradeId and covers the whole open position. A limit order adds limitPriceCents. Unknown fields are refused (400), so a typo never changes an order.

type

enum<string>

required

market: fills now at the live price or is refused. limit: fills at limitPriceCents or better, or rests (gtc), or is canceled (ioc, fok).

Available options:

market,

limit

idempotencyKey

string<uuid>

required

One per order. The same key again answers the stored order with replayed: true and places nothing; the same key with a different order is 409 idempotency_key_reused. Retry with the same key after a timeout or a 503.

action

enum<string>

default:buy

Available options:

buy,

sell

clientOrderId

string<uuid>

Kalshi's name for idempotencyKey. Send one of the two.

instrumentId

string

Buy: the Arena instrument; side is the instrument's side. It must list on one live Kalshi market (409 no_tradable_listing otherwise).

Pattern: ^ins_[0-9A-HJKMNP-TV-Z]{12}$

ticker

string

Buy: a Kalshi market ticker instead of instrumentId; side is the market's side. Never echoed back while the venue-data switch is off.

side

enum<string>

Buy: the side to buy.

Available options:

yes,

no

count

integer

Buy: contracts. Your paper balance is the limit.

Required range: 1 <= x <= 1000000000

tradeId

string<uuid>

Sell: the open position (GET /portfolio).

limitPriceCents

integer

Limit: your price for the side you trade, in cents (a percent).

Required range: 1 <= x <= 99

timeInForce

enum<string>

default:gtc

Available options:

gtc,

ioc,

fok,

good_till_canceled,

immediate_or_cancel,

fill_or_kill

expiresAt

string<date-time>

gtc only: when the order stops resting. At most 365 days out.

maxPriceCents

integer

Market buy: refuse to fill above this (409 price_moved, nothing placed).

Required range: 1 <= x <= 99

minPriceCents

integer

Market sell: refuse to sell below this (409 price_moved, nothing sold).

Required range: 1 <= x <= 99

route

enum<string>

best: a fill may be priced at Novig's or Polymarket's price when it passes every check. Omitted: Kalshi's.

Available options:

kalshi,

best

statedProbPct

integer

Buy: your probability for the side. Never changes the fill; scored on /eval.

Required range: 1 <= x <= 99

Response

A replay: this idempotencyKey was used before for the same order. Nothing new was placed.

status

enum<string>

required

canceled: an ioc or fok that did not fill. Nothing was spent.

Available options:

executed,

resting,

canceled

action

enum<string>

required

Available options:

buy,

sell

type

enum<string>

required

Available options:

market,

limit

idempotencyKey

string<uuid>

required

replayed

boolean

required

True when this idempotencyKey was used before: the stored order, nothing new placed.

originalCreatedAt

string<date-time> | null

required

On a replay: when the order was first placed.

order

object | null

required

The limit order. Null for a market order, which is a fill and not an order.

Show child attributes

trade

object | null

required

The position opened (buy) or closed (sell). Null while resting or canceled.

Show child attributes

fillVenue

enum<string> | null

required

Where the fill was priced. Paper only: nothing is sent there.

Available options:

kalshi,

novig,

polymarket,

null

mode

string

required

Allowed value: "paper"

venueData

boolean

required

fillPriceCents

integer | null

Only while the venue-data switch is on.

Status

Identity

API keys

Usage

Records

Portfolio

Markets

Trading

Place a paper order

Authorizations

Body

Response