Create Combo

REST APIs Prediction Markets CombosCreate Combo

Create Combo

POSThttps://api.gemini.com/v1/prediction-markets/combos

Create a canonical two-to-six-leg Prediction Markets combo, or retrieve the same combo when its complete leg set already exists.

Production availability

This Combo Prediction Markets endpoint is not currently enabled in production.

POSTv1/prediction-markets/combos

curl --request POST \
  --url https://api.gemini.com/v1/prediction-markets/combos \
  --header 'Content-Type: application/json' \
  --header 'X-GEMINI-APIKEY: <string>' \
  --header 'X-GEMINI-PAYLOAD: <string>' \
  --header 'X-GEMINI-SIGNATURE: <string>' \
  --data '
{
  "legs": [
    {
      "contractId": "101",
      "requiredOutcome": "Yes"
    },
    {
      "contractId": "202",
      "requiredOutcome": "No"
    }
  ]
}
'

Access

This endpoint requires signed private REST authentication, the

Code

PredictionsNewOrder

permission, and an unrestricted trading account. The account is derived from the authenticated API key; do not include an account ID in the request.

Canonicalization

The complete set of legs defines a combo. Reordering the same legs does not create another combo: a new canonical combo returns

Code

201

with

Code

alreadyExisted: false

, while an existing one returns

Code

200

with

Code

alreadyExisted: true

Headers

X-GEMINI-APIKEYstring·required

Your API key

X-GEMINI-SIGNATUREstring·required

HEX-encoded HMAC-SHA384 of payload signed with API secret

X-GEMINI-PAYLOADstring·required

Base64-encoded JSON payload

Content-Typestring

Default: text/plain

Content-Lengthstring

Default: 0

Cache-Controlstring

Default: no-cache

Request Body

legsarray·required

Two to six distinct underlying contract legs. The service canonicalizes their complete set, so leg order does not create a distinct combo.

legs[].contractIdstring·required

Underlying contract ID as a decimal string.Example: 101

legs[].requiredOutcomestring·enum·required

Required settlement outcome for this leg.Enum values: YesNoExample: Yes

Responses

The canonical combo already exists.

comboobject·required

combo.idinteger (int64)·required

Internal combo ID.Example: 456

combo.canonicalLegKeystring·required

Canonical identity of the complete combo leg set.Example: 101:Yes|202:No

combo.legCountinteger (int32)·required

Number of legs in the combo.Example: 2

combo.displayNamestring

Human-readable combo name, when available.

combo.statusstring

Current combo status, when available.

combo.instrumentIdinteger (int64)

Associated instrument ID, when available.

combo.instrumentSymbolstring

Associated instrument symbol, when available.Example: GEMI-CMB-0526-A7F3B2C1D4E5

combo.instrumentRegisteredboolean·required

Whether the combo has been registered with an instrument symbol.

combo.latestExpiryDatestring (date-time)

Latest expiry among the underlying legs, when available.

combo.createdAtstring (date-time)

Creation time, when available.

combo.updatedAtstring (date-time)

Most recent update time, when available.

combo.legsarray·required

Canonically ordered combo legs.

combo.legs[].comboIdinteger (int64)·required

Parent combo ID.

combo.legs[].legIndexinteger (int32)·required

Zero-based leg position in canonical order.

combo.legs[].contractIdstring·required

Underlying contract ID as a decimal string.

combo.legs[].requiredOutcomestring·enum·required

Required settlement outcome for the leg.Enum values: YesNo

combo.legs[].legOutcomestring·enum

Settled outcome for the leg, when resolved.Enum values: YesNo

combo.legs[].resolvedAtstring (date-time)

Resolution time for the leg, when resolved.

combo.legs[].contractobject

Underlying contract metadata, when available.

combo.legs[].contract.contractIdstring

combo.legs[].contract.contractNamestring

combo.legs[].contract.contractTickerstring

combo.legs[].contract.eventTickerstring

combo.legs[].contract.eventNamestring

combo.legs[].contract.categorystring

combo.legs[].contract.contractStatusstring

combo.legs[].contract.eventTypestring

Event type ("binary" or "categorical")

combo.legs[].contract.expiryDatestring (date-time)

combo.legs[].contract.resolvedAtstring (date-time)

combo.legs[].contract.resolutionSidestring

Winning outcome if resolved ("yes" or "no")

combo.legs[].contract.parentEventTickerstring

Parent event ticker for sub-events

combo.legs[].contract.startTimestring (date-time)

Start datetime (ISO 8601)

alreadyExistedboolean·required

`false` when this request created the canonical combo; `true` when the canonical combo already existed.

PreviousGet Combo

Last modified on August 10, 2026

curl --request POST \ --url https://api.gemini.com/v1/prediction-markets/combos \ --header 'Content-Type: application/json' \ --header 'X-GEMINI-APIKEY: <string>' \ --header 'X-GEMINI-PAYLOAD: <string>' \ --header 'X-GEMINI-SIGNATURE: <string>' \ --data ' { "legs": [ { "contractId": "101", "requiredOutcome": "Yes" }, { "contractId": "202", "requiredOutcome": "No" } ] } '

Request Body

legsarray·required

Two to six distinct underlying contract legs. The service canonicalizes their complete set, so leg order does not create a distinct combo.

legs[].contractIdstring·required

Underlying contract ID as a decimal string.Example: 101

legs[].requiredOutcomestring·enum·required

Required settlement outcome for this leg.Enum values: YesNoExample: Yes

Responses

The canonical combo already exists.

comboobject·required

combo.idinteger (int64)·required

Internal combo ID.Example: 456

combo.canonicalLegKeystring·required

Canonical identity of the complete combo leg set.Example: 101:Yes|202:No

combo.legCountinteger (int32)·required

Number of legs in the combo.Example: 2

combo.displayNamestring

Human-readable combo name, when available.

combo.statusstring

Current combo status, when available.

combo.instrumentIdinteger (int64)

Associated instrument ID, when available.

combo.instrumentSymbolstring

Associated instrument symbol, when available.Example: GEMI-CMB-0526-A7F3B2C1D4E5

combo.instrumentRegisteredboolean·required

Whether the combo has been registered with an instrument symbol.

combo.latestExpiryDatestring (date-time)

Latest expiry among the underlying legs, when available.

combo.createdAtstring (date-time)

Creation time, when available.

combo.updatedAtstring (date-time)

Most recent update time, when available.

combo.legsarray·required

Canonically ordered combo legs.

combo.legs[].comboIdinteger (int64)·required

Parent combo ID.

combo.legs[].legIndexinteger (int32)·required

Zero-based leg position in canonical order.

combo.legs[].contractIdstring·required

Underlying contract ID as a decimal string.

combo.legs[].requiredOutcomestring·enum·required

Required settlement outcome for the leg.Enum values: YesNo

combo.legs[].legOutcomestring·enum

Settled outcome for the leg, when resolved.Enum values: YesNo

combo.legs[].resolvedAtstring (date-time)

Resolution time for the leg, when resolved.

combo.legs[].contractobject

Underlying contract metadata, when available.

combo.legs[].contract.contractIdstring

combo.legs[].contract.contractNamestring

combo.legs[].contract.contractTickerstring

combo.legs[].contract.eventTickerstring

combo.legs[].contract.eventNamestring

combo.legs[].contract.categorystring

combo.legs[].contract.contractStatusstring

combo.legs[].contract.eventTypestring

Event type ("binary" or "categorical")

combo.legs[].contract.expiryDatestring (date-time)

combo.legs[].contract.resolvedAtstring (date-time)

combo.legs[].contract.resolutionSidestring

Winning outcome if resolved ("yes" or "no")

combo.legs[].contract.parentEventTickerstring

Parent event ticker for sub-events

combo.legs[].contract.startTimestring (date-time)

Start datetime (ISO 8601)

alreadyExistedboolean·required

`false` when this request created the canonical combo; `true` when the canonical combo already existed.