Markets and Trading

Understand binary markets, YES-side pricing, order matching, positions, and the order instructions available through UDX.

An event is a real-world proposition with a YES or NO outcome. A market is the tradable contract whose settlement direction derives from one or more event outcomes. Trading always uses the YES contract.

Market Structure

Term	Meaning
Series	A recurring family of events.
Event	The real-world question that resolves YES or NO.
Market	The tradable contract and its order book.
Contract	The quantity being bought or sold.

A single-leg market derives its settlement direction from one event outcome. A multi-leg market combines selected YES or NO outcomes from two or more component markets. Both are markets with their own ticker and order book; “market” throughout these docs includes both unless a restriction is stated.

A winning contract settles to $1.00. A losing contract settles to $0.00.

Provider Identifiers

A market may carry external_ids: the identifiers it has in third-party data providers’ systems, grouped by provider. Use it to join UDX markets onto a provider’s feed instead of matching on tickers or descriptions. The object is omitted when a market has no recorded provider identifiers, and a change to it is published as a market_metadata_updated event. A multi-leg market has no fixture of its own; each entry in its legs carries that component market’s external_ids instead.

Listing Details

A market may carry series_ticker, the series it is listed under, and event_ticker, which groups the markets for one game or contest within that series. title, rules, opens_at, notional_value, and contract_terms_url describe the contract it trades. Each is omitted when the market has no value for it, and a change to any of them is published as a market_metadata_updated event.

rules is the authority on how a market resolves. strike summarizes its threshold: value is the threshold itself, type names the comparison, and unit says how to read value. type is omitted when the comparison has no name below.

Type	Comparison
`greater`	Greater than the strike
`greater_or_equal`	Greater than or equal to the strike
`less`	Less than the strike
`less_or_equal`	Less than or equal to the strike
`equal`	Equal to the strike

Unit	Value
`decimal`	A number that can have a fractional part, such as `1.5`
`integer`	A whole number
`points`	A number of points, such as a points total
`string`	Text, such as a team name
`bool`	`true` or `false`
`unknown`	A unit not listed here; read `rules` for how to interpret `value`

Trade the YES Contract

BUY YES opens or adds to a long position.
SELL YES opens or adds to a short position.

There is no separate NO contract. Buying NO at $0.40 is economically equivalent to selling YES at $0.60.

A position is the signed net quantity of YES contracts. Positive is long YES; negative is short YES.

Prices and Quantities

Prices are in dollars in YES price space and must follow the market’s tick_size. Markets tick in deci-cents (0.001), so never assume whole cents. Quantities are in contracts with at most two decimal places, so the smallest order is 0.01 contracts.

Use decimal strings from the API for price and quantity calculations. Do not convert them to binary floating-point values.

Orders and Trades

An order remains open until it matches, expires, or is canceled. A match creates a trade and updates the account’s position. Whether a market accepts orders at all depends on its lifecycle status.

See Order Entry for time in force, post-only, self-trade prevention, and how orders are placed, amended, and canceled.