Public endpoints for discovering and inspecting combo contracts, plus an authenticated endpoint to create or retrieve a canonical combo. Combos are multi-leg contracts; order entry uses the same place/cancel endpoints as single contracts.
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openapi: 3.2.0
info:
title: Gemini Prediction Markets Combos API
description: 'API for trading prediction market contracts on Gemini.
**Note:** Only fields documented in this specification are considered stable. Undocumented fields in API responses may change or be removed without notice.'
version: 1.0.0
contact:
name: Gemini API Support
servers:
- url: https://api.gemini.com
description: Production
- url: https://api.sandbox.gemini.com
description: Sandbox
tags:
- name: Combos
description: Public endpoints for discovering and inspecting combo contracts, plus an authenticated endpoint to create or retrieve a canonical combo. Combos are multi-leg contracts; order entry uses the same place/cancel endpoints as single contracts.
paths:
/v1/prediction-markets/combos:
get:
tags:
- Combos
summary: List combo contracts
description: Returns a paginated list of combo contracts. Each combo includes its full leg breakdown and per-leg resolution status. When `status` is omitted, the endpoint returns only `Active` combos. This Combo Prediction Markets endpoint is not currently enabled in production.
operationId: listCombos
parameters:
- name: status
in: query
required: false
description: Filter by combo contract status (for example, `Active`, `Settled`, or `Voided`). Defaults to `Active` when omitted.
schema:
type: string
- name: contractId
in: query
required: false
description: Filter to combos that contain a specific underlying contract ID as a leg
schema:
type: integer
format: int64
- name: instrumentRegistered
in: query
required: false
description: Filter by whether the combo has been registered with an instrument symbol
schema:
type: boolean
- $ref: '#/components/parameters/Limit'
- $ref: '#/components/parameters/Offset'
responses:
'200':
description: Successful response
content:
application/json:
schema:
$ref: '#/components/schemas/ListCombosResponse'
examples:
activeCombos:
summary: List of active combo contracts
value:
combos:
- contract:
contractId: '456'
contractName: BTC EOY26 > $120k AND ETH EOY26 > $4k
contractTicker: GEMI-CMB-0526-A7F3B2C1D4E5
eventTicker: GEMI-CMB-0526-A7F3B2C1D4E5
eventName: BTC EOY26 > $120k AND ETH EOY26 > $4k
category: Combo
contractStatus: Active
eventType: binary
expiryDate: '2026-12-31T23:59:59Z'
resolvedAt: null
resolutionSide: null
parentEventTicker: null
startTime: null
legs:
- comboId: 456
legIndex: 0
contractId: '101'
requiredOutcome: 'Yes'
legOutcome: null
resolvedAt: null
contract:
contractId: '101'
contractName: BTC above $120,000 at year-end 2026
contractTicker: GEMI-BTC-EOY26-HI120000
eventTicker: GEMI-BTC-EOY26
eventName: Bitcoin Year-End 2026
category: Crypto
contractStatus: Active
eventType: binary
expiryDate: '2026-12-31T23:59:59Z'
resolvedAt: null
resolutionSide: null
parentEventTicker: null
startTime: null
- comboId: 456
legIndex: 1
contractId: '202'
requiredOutcome: 'Yes'
legOutcome: null
resolvedAt: null
contract:
contractId: '202'
contractName: ETH above $4,000 at year-end 2026
contractTicker: GEMI-ETH-EOY26-HI4000
eventTicker: GEMI-ETH-EOY26
eventName: Ethereum Year-End 2026
category: Crypto
contractStatus: Active
eventType: binary
expiryDate: '2026-12-31T23:59:59Z'
resolvedAt: null
resolutionSide: null
parentEventTicker: null
startTime: null
pagination:
limit: 50
offset: 0
total: 1
'400':
$ref: '#/components/responses/BadRequest'
'500':
$ref: '#/components/responses/InternalError'
'503':
$ref: '#/components/responses/ServiceUnavailable'
post:
tags:
- Combos
summary: Create or retrieve a canonical combo
description: 'Creates a combo from two to six underlying contract legs for the authenticated account. The service canonicalizes the complete leg set, so submitting the same legs again returns the existing combo regardless of leg order. The account is derived from the authenticated API key; do not include an account ID in the request. This Combo Prediction Markets endpoint is not currently enabled in production.
Requires signed private REST authentication, the `PredictionsNewOrder` permission, and an unrestricted trading account. A new canonical combo returns `201 Created` with `alreadyExisted: false`; an existing canonical combo returns `200 OK` with `alreadyExisted: true`.'
operationId: createCombo
security:
- apiKey: []
payloadAuth: []
signatureAuth: []
requestBody:
required: true
content:
application/json:
schema:
$ref: '#/components/schemas/CreateComboRequest'
examples:
twoLegCombo:
summary: Create a two-leg combo
value:
legs:
- contractId: '101'
requiredOutcome: 'Yes'
- contractId: '202'
requiredOutcome: 'No'
responses:
'200':
description: The canonical combo already exists.
content:
application/json:
schema:
$ref: '#/components/schemas/CreateComboResponse'
examples:
existingCombo:
summary: Existing canonical combo
value:
combo:
id: 456
canonicalLegKey: 101:Yes|202:No
legCount: 2
displayName: BTC EOY26 > $120k AND ETH EOY26 <= $4k
status: Active
instrumentId: 98765
instrumentSymbol: GEMI-CMB-0526-A7F3B2C1D4E5
instrumentRegistered: true
latestExpiryDate: '2026-12-31T23:59:59.000Z'
createdAt: '2026-05-01T12:00:00.000Z'
updatedAt: '2026-05-01T12:00:00.000Z'
legs:
- comboId: 456
legIndex: 0
contractId: '101'
requiredOutcome: 'Yes'
- comboId: 456
legIndex: 1
contractId: '202'
requiredOutcome: 'No'
alreadyExisted: true
'201':
description: A new canonical combo was created.
content:
application/json:
schema:
$ref: '#/components/schemas/CreateComboResponse'
examples:
createdCombo:
summary: New canonical combo
value:
combo:
id: 456
canonicalLegKey: 101:Yes|202:No
legCount: 2
displayName: BTC EOY26 > $120k AND ETH EOY26 <= $4k
status: Active
instrumentId: 98765
instrumentSymbol: GEMI-CMB-0526-A7F3B2C1D4E5
instrumentRegistered: true
latestExpiryDate: '2026-12-31T23:59:59.000Z'
createdAt: '2026-05-01T12:00:00.000Z'
updatedAt: '2026-05-01T12:00:00.000Z'
legs:
- comboId: 456
legIndex: 0
contractId: '101'
requiredOutcome: 'Yes'
- comboId: 456
legIndex: 1
contractId: '202'
requiredOutcome: 'No'
alreadyExisted: false
'400':
description: The request body is malformed or fails combo validation.
content:
application/json:
schema:
$ref: '#/components/schemas/ComboWriteError'
example:
error: InvalidInput
code: COMBO_VALIDATION_ERROR
message: a combo needs 2-6 legs
'401':
description: Signed private REST authentication is missing or invalid.
content:
application/json:
schema:
$ref: '#/components/schemas/AuthErrorResponse'
'403':
description: The API key lacks `PredictionsNewOrder`, or the authenticated trading account is restricted.
content:
application/json:
schema:
$ref: '#/components/schemas/AuthErrorResponse'
'404':
description: Combos are unavailable, or an underlying contract in the request cannot be found.
content:
application/json:
schema:
$ref: '#/components/schemas/ComboWriteError'
examples:
comboUnavailable:
summary: Combos unavailable
value:
error: NOT_FOUND
message: Not Found
legNotFound:
summary: Underlying contract not found
value:
error: NOT_FOUND
code: COMBO_LEG_NOT_FOUND
message: One or more contracts in this combo could not be found. Update your selection and try again.
'500':
description: An unexpected error occurred while creating the combo.
content:
application/json:
schema:
$ref: '#/components/schemas/ComboWriteError'
example:
error: InternalError
message: An unexpected error occurred
/v1/prediction-markets/combos/{instrumentSymbol}:
get:
tags:
- Combos
summary: Get combo by instrument symbol
description: Returns the full specification of a single combo contract identified by its instrument symbol, including leg breakdown and per-leg resolution status. This Combo Prediction Markets endpoint is not currently enabled in production.
operationId: getComboByInstrumentSymbol
parameters:
- name: instrumentSymbol
in: path
required: true
description: The combo contract's instrument symbol (e.g. `GEMI-CMB-0526-A7F3B2C1D4E5`)
schema:
type: string
example: GEMI-CMB-0526-A7F3B2C1D4E5
responses:
'200':
description: Successful response
content:
application/json:
schema:
$ref: '#/components/schemas/ComboResponse'
examples:
comboDetail:
summary: Combo contract detail
value:
contract:
contractId: '456'
contractName: BTC EOY26 > $120k AND ETH EOY26 > $4k
contractTicker: GEMI-CMB-0526-A7F3B2C1D4E5
eventTicker: GEMI-CMB-0526-A7F3B2C1D4E5
eventName: BTC EOY26 > $120k AND ETH EOY26 > $4k
category: Combo
contractStatus: Active
eventType: binary
expiryDate: '2026-12-31T23:59:59Z'
resolvedAt: null
resolutionSide: null
parentEventTicker: null
startTime: null
legs:
- comboId: 456
legIndex: 0
contractId: '101'
requiredOutcome: 'Yes'
legOutcome: null
resolvedAt: null
contract:
contractId: '101'
contractName: BTC above $120,000 at year-end 2026
contractTicker: GEMI-BTC-EOY26-HI120000
eventTicker: GEMI-BTC-EOY26
eventName: Bitcoin Year-End 2026
category: Crypto
contractStatus: Active
eventType: binary
expiryDate: '2026-12-31T23:59:59Z'
resolvedAt: null
resolutionSide: null
parentEventTicker: null
startTime: null
- comboId: 456
legIndex: 1
contractId: '202'
requiredOutcome: 'Yes'
legOutcome: null
resolvedAt: null
contract:
contractId: '202'
contractName: ETH above $4,000 at year-end 2026
contractTicker: GEMI-ETH-EOY26-HI4000
eventTicker: GEMI-ETH-EOY26
eventName: Ethereum Year-End 2026
category: Crypto
contractStatus: Active
eventType: binary
expiryDate: '2026-12-31T23:59:59Z'
resolvedAt: null
resolutionSide: null
parentEventTicker: null
startTime: null
'404':
description: Combo not found
content:
application/json:
schema:
$ref: '#/components/schemas/Error'
example:
error: NOT_FOUND
message: Combo not found
'500':
$ref: '#/components/responses/InternalError'
'503':
$ref: '#/components/responses/ServiceUnavailable'
components:
schemas:
ListCombosResponse:
type: object
required:
- combos
- pagination
properties:
combos:
type: array
description: List of combo contracts matching the query
items:
$ref: '#/components/schemas/ComboResponse'
pagination:
allOf:
- $ref: '#/components/schemas/Pagination'
AuthErrorResponse:
type: object
additionalProperties: false
required:
- result
- reason
- message
properties:
result:
type: string
enum:
- error
reason:
type: string
description: Authentication or authorization error class
example: MissingNonce
message:
type: string
description: Human-readable authentication or authorization detail
example: Must provide unique monotonic increasing 'nonce' field in payload
CreateComboRequest:
type: object
description: A canonical combo definition. The authenticated account is derived from the signed request and is not a request field.
required:
- legs
properties:
legs:
type: array
description: Two to six distinct underlying contract legs. The service canonicalizes their complete set, so leg order does not create a distinct combo.
minItems: 2
maxItems: 6
items:
$ref: '#/components/schemas/CreateComboLeg'
Pagination:
type: object
properties:
limit:
type: integer
example: 50
offset:
type: integer
example: 0
total:
type: integer
example: 100
ComboResponse:
type: object
required:
- contract
- legs
properties:
contract:
allOf:
- $ref: '#/components/schemas/ContractMetadata'
description: Metadata for the combo contract itself (ticker, status, expiry, etc.)
legs:
type: array
description: Ordered list of legs that make up this combo
items:
$ref: '#/components/schemas/ComboLeg'
ComboSummary:
type: object
required:
- id
- canonicalLegKey
- legCount
- instrumentRegistered
- legs
properties:
id:
type: integer
format: int64
description: Internal combo ID.
example: 456
canonicalLegKey:
type: string
description: Canonical identity of the complete combo leg set.
example: 101:Yes|202:No
legCount:
type: integer
format: int32
description: Number of legs in the combo.
example: 2
displayName:
type: string
description: Human-readable combo name, when available.
status:
type: string
description: Current combo status, when available.
instrumentId:
type: integer
format: int64
description: Associated instrument ID, when available.
instrumentSymbol:
type: string
description: Associated instrument symbol, when available.
example: GEMI-CMB-0526-A7F3B2C1D4E5
instrumentRegistered:
type: boolean
description: Whether the combo has been registered with an instrument symbol.
latestExpiryDate:
type: string
format: date-time
description: Latest expiry among the underlying legs, when available.
createdAt:
type: string
format: date-time
description: Creation time, when available.
updatedAt:
type: string
format: date-time
description: Most recent update time, when available.
legs:
type: array
description: Canonically ordered combo legs.
items:
$ref: '#/components/schemas/ComboSummaryLeg'
Error:
type: object
properties:
error:
type: string
description: Error code
example: InvalidInput
message:
type: string
description: Human-readable error message
example: orderId is required
ComboWriteError:
type: object
required:
- error
- message
properties:
error:
type: string
description: Error class.
example: InvalidInput
code:
type: string
description: Machine-readable code for validation or missing-leg errors, when available.
example: COMBO_VALIDATION_ERROR
message:
type: string
description: Human-readable error detail.
example: a combo needs 2-6 legs
ContractMetadata:
type: object
properties:
contractId:
type: string
contractName:
type: string
contractTicker:
type: string
eventTicker:
type: string
eventName:
type: string
category:
type: string
contractStatus:
type: string
eventType:
type: string
description: Event type ("binary" or "categorical")
expiryDate:
type:
- string
- 'null'
format: date-time
resolvedAt:
type:
- string
- 'null'
format: date-time
resolutionSide:
type:
- string
- 'null'
description: Winning outcome if resolved ("yes" or "no")
parentEventTicker:
type:
- string
- 'null'
description: Parent event ticker for sub-events
startTime:
type:
- string
- 'null'
format: date-time
description: Start datetime (ISO 8601)
CreateComboLeg:
type: object
required:
- contractId
- requiredOutcome
properties:
contractId:
type: string
description: Underlying contract ID as a decimal string.
example: '101'
requiredOutcome:
type: string
enum:
- 'Yes'
- 'No'
description: Required settlement outcome for this leg.
example: 'Yes'
ComboSummaryLeg:
type: object
required:
- comboId
- legIndex
- contractId
- requiredOutcome
properties:
comboId:
type: integer
format: int64
description: Parent combo ID.
legIndex:
type: integer
format: int32
description: Zero-based leg position in canonical order.
contractId:
type: string
description: Underlying contract ID as a decimal string.
requiredOutcome:
type: string
enum:
- 'Yes'
- 'No'
description: Required settlement outcome for the leg.
legOutcome:
type:
- string
- 'null'
enum:
- 'Yes'
- 'No'
description: Settled outcome for the leg, when resolved.
resolvedAt:
type:
- string
- 'null'
format: date-time
description: Resolution time for the leg, when resolved.
contract:
allOf:
- $ref: '#/components/schemas/ContractMetadata'
description: Underlying contract metadata, when available.
CreateComboResponse:
type: object
required:
- combo
- alreadyExisted
properties:
combo:
$ref: '#/components/schemas/ComboSummary'
alreadyExisted:
type: boolean
description: '`false` when this request created the canonical combo; `true` when the canonical combo already existed.'
ComboLeg:
type: object
required:
- comboId
- legIndex
- contractId
- requiredOutcome
properties:
comboId:
type: integer
format: int64
description: Internal ID of the parent combo contract
example: 456
legIndex:
type: integer
description: Zero-based position of this leg in the combo
example: 0
contractId:
type: string
description: Internal ID of the underlying single contract, represented as a decimal string
example: '101'
requiredOutcome:
type: string
enum:
- 'Yes'
- 'No'
description: The outcome this leg must settle for the combo to settle YES
example: 'Yes'
legOutcome:
type:
- string
- 'null'
description: The outcome this leg has settled to, if resolved (`"Yes"` or `"No"`). Null while the leg is still active.
example: null
resolvedAt:
type:
- string
- 'null'
format: date-time
description: UTC timestamp when this leg resolved. Null while still active.
example: null
contract:
allOf:
- $ref: '#/components/schemas/ContractMetadata'
description: Full metadata for the underlying single contract
parameters:
Offset:
name: offset
in: query
description: Number of results to skip for pagination
schema:
type: integer
default: 0
minimum: 0
Limit:
name: limit
in: query
description: Maximum number of results to return (max 500)
schema:
type: integer
default: 50
minimum: 1
maximum: 500
responses:
InternalError:
description: Internal server error
content:
application/json:
schema:
$ref: '#/components/schemas/Error'
ServiceUnavailable:
description: Prediction markets feature is temporarily unavailable
content:
application/json:
schema:
$ref: '#/components/schemas/Error'
BadRequest:
description: Invalid request parameters
content:
application/json:
schema:
$ref: '#/components/schemas/Error'
securitySchemes:
apiKey:
type: apiKey
in: header
name: X-GEMINI-APIKEY
description: Gemini API key with appropriate permissions
payloadAuth:
type: apiKey
in: header
name: X-GEMINI-PAYLOAD
description: Base64-encoded private REST payload. See Gemini private REST authentication.
signatureAuth:
type: apiKey
in: header
name: X-GEMINI-SIGNATURE
description: Hex HMAC-SHA384 signature of the payload using the API secret.