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Amend an Order

Amends a resting order in place, changing its price and/or quantity. Side and time in force are unchanged. Queue priority is preserved only when quantity strictly decreases at an unchanged price.

POST/orders/{order_id}/amend
Authorization
UDX-Access-KeyAPI key · headerrequired
Opaque API key ID.
UDX-Access-TimestampAPI key · headerrequired
Unix time in milliseconds, within 30 seconds of server time.
UDX-Access-SignatureAPI key · headerrequired
Standard-base64 RSA-PSS/SHA-256 signature with a 32-byte salt. Sign `timestamp + METHOD + path`; for requests with a body, append `hex(SHA256(body))`; append `UDX-Idempotency-Key` when it is present.
or
AuthorizationBearer token (JWT) · headerrequired
Bearer token for an active signed-in UDX user.
Path parameters
order_idExchangeIdrequired
Exchange-assigned order identifier.
min length 1 · max length 64
Header parameters
UDX-Versionstring
Dated API version (YYYY-MM-DD). Omit to use the oldest supported version. An unknown version returns `400`.
max length 10
UDX-Idempotency-Keystring
Optional client-generated key that makes a mutation safe to retry. Reuse it only for a byte-identical retry. When present, it is included in the request signature; omitting it disables UDX idempotency for that request.
min length 1 · max length 255
Request body
requiredapplication/json
tickerTickerrequired
A market identifier (ticker) — a human-meaningful natural-key symbol, not a UUID. Unique per market.
min length 1 · max length 128
quantityobjectrequired
New total order quantity, in contracts (absolute, not a delta). Must exceed the quantity already filled.
Show properties
object
priceobjectrequired
New limit price in YES price space, in dollars.
Show properties
object
client_order_idobject
The existing order's client_order_id, for the caller's reference (the order is identified by the order_id path parameter).
Show properties
object
updated_client_order_idobject
New correlation id for the amended order. The order keeps its existing client_order_id when omitted.
Show properties
object
Responses
200The amended order.
orderOrderrequired
An order on the exchange, priced from the YES side.
Show properties
order_idobjectrequired
Exchange-assigned order identifier.
Show properties
object
client_order_idobject
The caller's correlation id for this order.
Show properties
object
tickerTickerrequired
A market identifier (ticker) — a human-meaningful natural-key symbol, not a UUID. Unique per market.
min length 1 · max length 128
sideOrderSiderequired
Order side. `buy` buys YES, `sell` sells YES — everything is priced from the YES side. (Selling YES is economically equivalent to buying NO at 1 − price.)
Allowed:buysell
quantityobjectrequired
Order quantity, in contracts.
Show properties
object
priceobjectrequired
Limit price in YES price space, in dollars, regardless of side.
Show properties
object
time_in_forceOrderTimeInForcerequired
The time-in-force reported on an order. Adds `unknown` to the placement values (`TimeInForce`): the exchange may report it for an order that reached the account through another channel with a time-in-force UDX does not model, so the order stays readable. `unknown` is read-only and is never accepted when placing an order.
Allowed:gtciocfokdayunknown
statusOrderStatusrequired
An order's status. `rejected` means the exchange rejected it; `canceled` covers user cancels and expiries.
Allowed:restingpartially_filledfilledcanceledrejected
filled_quantityobjectrequired
The quantity of the order that has been filled.
Show properties
object
remaining_quantityobjectrequired
The quantity of the order that is currently resting.
Show properties
object
average_fill_priceobject
Volume-weighted average fill price. Present when filled_quantity > 0.
Show properties
object
fees_paidobjectrequired
Total fees (commission) collected on the order so far, in dollars.
Show properties
object
created_atstring<date-time>required
When the order was created. UDX timestamps use RFC 3339; requests require an explicit UTC offset and zero to six fractional digits; responses use UTC with exactly six fractional digits.
max length 40
400The request doesn't conform to this spec.
typestring<uri-reference>
A stable URI identifying the error's general category. Usually absent (equivalent to "about:blank" per the RFC); documented rate controls use closed URN values so callers can distinguish same-status retry causes without parsing localized prose.
max length 2048
titlestringrequired
A localized, human-readable summary of the error category. Stable for a given status code and resolved language — clients must not use it as a machine-readable discriminator.
max length 40
statusintegerrequired
The HTTP status code, repeated from the response itself.
detailstring
A localized, human-readable explanation specific to this occurrence. Clients must not parse it for machine-readable information.
max length 500
instancestring<uri-reference>
An identifier for this specific occurrence, so it can be correlated with server-side logs if you need to report it.
max length 100
401No valid credential was provided.
typestring<uri-reference>
A stable URI identifying the error's general category. Usually absent (equivalent to "about:blank" per the RFC); documented rate controls use closed URN values so callers can distinguish same-status retry causes without parsing localized prose.
max length 2048
titlestringrequired
A localized, human-readable summary of the error category. Stable for a given status code and resolved language — clients must not use it as a machine-readable discriminator.
max length 40
statusintegerrequired
The HTTP status code, repeated from the response itself.
detailstring
A localized, human-readable explanation specific to this occurrence. Clients must not parse it for machine-readable information.
max length 500
instancestring<uri-reference>
An identifier for this specific occurrence, so it can be correlated with server-side logs if you need to report it.
max length 100
404The requested resource doesn't exist or isn't visible to the caller.
typestring<uri-reference>
A stable URI identifying the error's general category. Usually absent (equivalent to "about:blank" per the RFC); documented rate controls use closed URN values so callers can distinguish same-status retry causes without parsing localized prose.
max length 2048
titlestringrequired
A localized, human-readable summary of the error category. Stable for a given status code and resolved language — clients must not use it as a machine-readable discriminator.
max length 40
statusintegerrequired
The HTTP status code, repeated from the response itself.
detailstring
A localized, human-readable explanation specific to this occurrence. Clients must not parse it for machine-readable information.
max length 500
instancestring<uri-reference>
An identifier for this specific occurrence, so it can be correlated with server-side logs if you need to report it.
max length 100
409This key is still in use or its response cannot be replayed. The mutation may have run; check `detail` before retrying.
typestring<uri-reference>
A stable URI identifying the error's general category. Usually absent (equivalent to "about:blank" per the RFC); documented rate controls use closed URN values so callers can distinguish same-status retry causes without parsing localized prose.
max length 2048
titlestringrequired
A localized, human-readable summary of the error category. Stable for a given status code and resolved language — clients must not use it as a machine-readable discriminator.
max length 40
statusintegerrequired
The HTTP status code, repeated from the response itself.
detailstring
A localized, human-readable explanation specific to this occurrence. Clients must not parse it for machine-readable information.
max length 500
instancestring<uri-reference>
An identifier for this specific occurrence, so it can be correlated with server-side logs if you need to report it.
max length 100
422This key belongs to a different request.
typestring<uri-reference>
A stable URI identifying the error's general category. Usually absent (equivalent to "about:blank" per the RFC); documented rate controls use closed URN values so callers can distinguish same-status retry causes without parsing localized prose.
max length 2048
titlestringrequired
A localized, human-readable summary of the error category. Stable for a given status code and resolved language — clients must not use it as a machine-readable discriminator.
max length 40
statusintegerrequired
The HTTP status code, repeated from the response itself.
detailstring
A localized, human-readable explanation specific to this occurrence. Clients must not parse it for machine-readable information.
max length 500
instancestring<uri-reference>
An identifier for this specific occurrence, so it can be correlated with server-side logs if you need to report it.
max length 100
429The Member's request rate is exhausted. Wait for `Retry-After`.
typestring<uri-reference>
A stable URI identifying the error's general category. Usually absent (equivalent to "about:blank" per the RFC); documented rate controls use closed URN values so callers can distinguish same-status retry causes without parsing localized prose.
max length 2048
titlestringrequired
A localized, human-readable summary of the error category. Stable for a given status code and resolved language — clients must not use it as a machine-readable discriminator.
max length 40
statusintegerrequired
The HTTP status code, repeated from the response itself.
detailstring
A localized, human-readable explanation specific to this occurrence. Clients must not parse it for machine-readable information.
max length 500
instancestring<uri-reference>
An identifier for this specific occurrence, so it can be correlated with server-side logs if you need to report it.
max length 100
500Something went wrong on UDX's side.
typestring<uri-reference>
A stable URI identifying the error's general category. Usually absent (equivalent to "about:blank" per the RFC); documented rate controls use closed URN values so callers can distinguish same-status retry causes without parsing localized prose.
max length 2048
titlestringrequired
A localized, human-readable summary of the error category. Stable for a given status code and resolved language — clients must not use it as a machine-readable discriminator.
max length 40
statusintegerrequired
The HTTP status code, repeated from the response itself.
detailstring
A localized, human-readable explanation specific to this occurrence. Clients must not parse it for machine-readable information.
max length 500
instancestring<uri-reference>
An identifier for this specific occurrence, so it can be correlated with server-side logs if you need to report it.
max length 100
503Request admission is unavailable. Retry later.
typestring<uri-reference>
A stable URI identifying the error's general category. Usually absent (equivalent to "about:blank" per the RFC); documented rate controls use closed URN values so callers can distinguish same-status retry causes without parsing localized prose.
max length 2048
titlestringrequired
A localized, human-readable summary of the error category. Stable for a given status code and resolved language — clients must not use it as a machine-readable discriminator.
max length 40
statusintegerrequired
The HTTP status code, repeated from the response itself.
detailstring
A localized, human-readable explanation specific to this occurrence. Clients must not parse it for machine-readable information.
max length 500
instancestring<uri-reference>
An identifier for this specific occurrence, so it can be correlated with server-side logs if you need to report it.
max length 100
Request
curl -X POST "https://{hostname}/orders/BK9BZNTK8022/amend" \
  -H "UDX-Access-Key: API_KEY_ID" \
  -H "UDX-Access-Timestamp: UNIX_MILLISECONDS" \
  -H "UDX-Access-Signature: BASE64_SIGNATURE" \
  -H "Content-Type: application/json" \
  -d '{
  "ticker": "UDX-EXAMPLE-MARKET",
  "quantity": "80",
  "price": "0.56"
}'
Response
{
  "order": {
    "order_id": "BK9BZNTK8022",
    "client_order_id": "order-20260804-001",
    "ticker": "UDX-EXAMPLE-MARKET",
    "side": "buy",
    "quantity": "80",
    "price": "0.56",
    "time_in_force": "gtc",
    "status": "resting",
    "filled_quantity": "0",
    "remaining_quantity": "80",
    "fees_paid": "0",
    "created_at": "2026-01-01T00:00:00.000000Z"
  }
}