Combos API Overview

A combo is a user-defined instrument with 2–50 legs. Each leg identifies an existing market symbol and whether the combo buys or sells that leg. Combo instruments can trade through normal order entry and can be used as the symbol of an RFQ. The public polymarket.v1.ComboAPI gRPC service creates and reads combo instruments. Each RPC also has a REST endpoint. REST JSON uses lower camel case; protobuf fields use snake case.

Endpoints

Method	Endpoint	Scope	Per-firm limit	Description
`GET`	`/v1/combos?symbol={symbol}`	`read:orders`	100 req/sec	Get a combo by exact symbol
`POST`	`/v1/combos`	`write:orders`	1 req/sec	Create or retrieve a combo for a set of legs

All calls require bearer-token authentication and an acting participant, supplied through x-participant-id or the token’s participant_id claim. Each method has a separate per-firm rate-limit bucket with one second of burst capacity. See Rate Limits. Separately, combo creation has a participant-wide service quota of 1,000 new instruments per week across all accounts and both Retail and Institutional APIs. The quota resets Monday at 00:00 UTC; returning an existing canonical combo does not consume it.

Create a Combo

POST /v1/combos accepts a list of 2–50 unique legs:

{
  "legs": [
    {
      "symbol": "aec-mlb-nyy-bos-2026-07-29-nyy",
      "side": "SIDE_BUY"
    },
    {
      "symbol": "tsc-nba-bos-lal-2026-07-29-207pt5",
      "side": "SIDE_SELL"
    }
  ]
}

The component symbols must be open, tradable, supported instruments. The service rejects duplicate symbols and invalid combinations. Treat the combo symbol as opaque: existing combos use caoc-... and new combos use crossd-.... Within one product, a canonical set of legs always maps to the same symbol; if that combo already exists, CreateCombo returns it.

{
  "combo": {
    "id": "caoc-...",
    "legs": [
      {
        "symbol": "aec-mlb-nyy-bos-2026-07-29-nyy",
        "side": "SIDE_BUY"
      },
      {
        "symbol": "tsc-nba-bos-lal-2026-07-29-207pt5",
        "side": "SIDE_SELL"
      }
    ],
    "state": "INSTRUMENT_STATE_OPEN",
    "createdTime": "2026-07-29T14:00:00Z",
    "tickSize": 0.001
  }
}

Get a Combo

GET /v1/combos?symbol=caoc-... requires the exact combo symbol and returns:

{
  "combos": [
    {
      "id": "caoc-...",
      "legs": [
        {
          "symbol": "aec-mlb-nyy-bos-2026-07-29-nyy",
          "side": "SIDE_BUY"
        },
        {
          "symbol": "tsc-nba-bos-lal-2026-07-29-207pt5",
          "side": "SIDE_SELL"
        }
      ],
      "state": "INSTRUMENT_STATE_OPEN",
      "createdTime": "2026-07-29T14:00:00Z",
      "tickSize": 0.001
    }
  ]
}

An unknown symbol returns an empty combos array. This endpoint does not paginate.

RFQ API

Create and manage combo RFQs and quotes

Combos/RFQ Guide

Maker workflow and quote rules

Authentication

OAuth metadata and required scopes

Rate Limits

Endpoint-level request limits

Overview

Health

Trading

Combos

RFQs

Report

Positions

Funding

Order Book

Settlement

Reference Data

Accounts

Payments

Incentives

Endpoints

Create a Combo

Get a Combo

See Also

RFQ API

Combos/RFQ Guide

Authentication

Rate Limits

​Endpoints

​Create a Combo

​Get a Combo

​See Also

RFQ API

Combos/RFQ Guide

Authentication

Rate Limits

Endpoints

Create a Combo

Get a Combo

See Also