Type Notation and Conventions

This page documents the type conventions used throughout the GX Exchange API documentation.

Primitive Types

Notation	Description	Example
`int`	Integer number, transmitted as a JSON number	`42`
`float`	Floating-point number, transmitted as a JSON number	`3.14`
`string`	UTF-8 string	`"BTC"`
`bool`	Boolean value	`true`
`address`	42-character hex-encoded Ethereum address with `0x` prefix	`"0x1234...abcd"`
`hex`	Hex-encoded byte string with `0x` prefix	`"0xdeadbeef"`

Numeric Strings

Prices, sizes, and monetary amounts are transmitted as strings to avoid floating-point precision loss. All arithmetic should be performed using fixed-point or decimal libraries.

{
  "p": "67432.5",
  "s": "0.001",
  "withdrawable": "12500.00"
}

Important: Never parse price or size fields as native floating-point numbers. Use BigNumber, Decimal, or equivalent in your language.

Composite Types

Notation	Description	Example
`Array<T>`	Ordered list of type T	`[1, 2, 3]`
`T?`	Optional field (may be absent or `null`)	`"c": "0x1a2b"` or absent
`Object`	A JSON object with documented fields	`{ "px": "100", "sz": "1.5" }`
`Map<K, V>`	Object used as a key-value map	`{ "BTC": "67432.5" }`
`[T, T]`	Fixed-length tuple	`[10000, 10001]`

Asset Identifiers

Context	Type	Description
Perpetual markets	`int`	Zero-based index from the `meta` endpoint universe array
Spot markets	`int`	Index from the `spotMeta` endpoint; spot indices begin at `10000`
Human-readable	`string`	Coin symbol such as `"BTC"`, `"ETH"`, or pair name `"BTC-USDC"`

See Asset IDs for the complete mapping.

Order Side Encoding

The API uses compact encodings for order sides:

Field	Buy	Sell
`b` (exchange endpoint)	`true`	`false`
`side` (info/fills)	`"B"`	`"A"`

The "A" and "B" convention maps to Ask (sell) and Bid (buy).

Time-in-Force Values

Value	Name	Description
`"Gtc"`	Good-til-cancelled	Rests on the book until filled or cancelled
`"Ioc"`	Immediate-or-cancel	Fills what is available immediately, cancels the remainder
`"Alo"`	Add-liquidity-only	Post-only order; rejected if it would cross the spread

Order Grouping

Value	Description
`"na"`	No grouping. Each order is independent.
`"normalTpsl"`	Take-profit / stop-loss group. Orders are linked.
`"positionTpsl"`	Position-level TP/SL. Attached to the entire position.

Timestamps

All timestamps in the API are Unix epoch in milliseconds unless otherwise noted:

{
  "time": 1700000000000,
  "nonce": 1700000000123,
  "startTime": 1700000000000,
  "endTime": 1700100000000
}

The one exception is the GX-API-TIMESTAMP header used for HMAC authentication, which uses seconds.

Pagination

Endpoints that return lists of historical data accept startTime and endTime parameters (milliseconds). Results are sorted by time in ascending order by default.

Null vs Absent

A field documented as optional (T?) may be omitted entirely from the JSON object or set to null.
Required fields are always present in responses.
Do not send null for required fields in requests; the server will reject the request with a 400 error.

String Number Precision

Field Type	Max Significant Figures	Example Valid	Example Invalid
Price (`p`, `px`, `limitPx`)	5	`"67432"`	`"67432.123"`
Size (`s`, `sz`)	Governed by `szDecimals`	`"0.00100"`	`"0.000001"` (if szDecimals=5)
Dollar amounts	8	`"12500.00"`	—

API Asset IDs