Symbology & Contract Identity

Symbols

A symbol identifies a stock, index, or option underlying: AAPL, SPY, SPX. Snapshot endpoints accept multiple symbols at once (a list in the SDKs, comma-separated over HTTP). Index option underlyings are distinct symbols per settlement style — SPX (AM-settled monthlies) and SPXW (PM-settled weeklies) are different roots; the same split applies to other index families (VIX/VIXW, NDX/NDXP). List the roots your account can see with the option symbols endpoint.

Option contract identity

An option contract is always the four-tuple (symbol, expiration, strike, right):

Part	Form	Example
symbol	underlying root	SPXW
expiration	YYYYMMDD date	20260618
strike	dollars, as a string	"5400" or "17.5"
right	C / P (call / put accepted)	C

Strikes are human dollars everywhere on the SDK surface — never scaled integers. Endpoints that take an optional strike / right treat omission as a wildcard: all strikes, both rights. Wildcard responses identify each row's contract via the expiration, strike, and right response fields.

The one place a scaled strike survives: the server's WebSocket subscribe envelope takes thousandths of a dollar (570000 = $570.00), matching the upstream wire convention.

Dates and times in

• Dates are YYYYMMDD strings ("20250303"). The HTTP server also accepts ISO YYYY-MM-DD.
• Date ranges are inclusive on both ends.
• Time-of-day inputs (start_time, end_time, time_of_day) are Eastern Time wall-clock HH:MM:SS (at-time endpoints take milliseconds: HH:MM:SS.SSS).
• interval accepts a preset (1s, 1m, 1h, …) or a millisecond count as a string ("60000").

Timestamps out

Response rows carry two integer time fields:

• date — the trading date as a YYYYMMDD integer.
• ms_of_day — milliseconds since midnight Eastern Time (34200000 = 09:30:00 ET).

Integer timestamps compare and bucket cheaply in hot loops; convert to wall-clock datetimes only at display boundaries.