spec-drift: probable — GET /book missing min_order_size, tick_size, neg_risk fields (order constraint data)

[realfishsam]

Exchange

probable (core/src/exchanges/probable/)

Spec file

core/specs/probable/probable.yaml

Summary

The live GET /public/api/v1/book response includes five top-level fields absent from the spec:

Field	Type	Significance
asset_id	string	token identifier for this book
timestamp	string	server-side timestamp of the snapshot
hash	string	book state hash
min_order_size	string	minimum valid order size for this market
tick_size	string	price tick increment for this market
neg_risk	boolean	whether this is a negatively-correlated risk market

The spec currently documents only { bids: array, asks: array, market: string } — the three newly-visible trading constraint fields are not captured in ProbableRawOrderBook.

Additionally, the bids and asks arrays are untyped in the spec. Live API returns elements shaped as { price: string, size: string } — the normalizer (normalizer.ts:59–64) already reads level.price and level.size with parseFloat, so the element shape is correct but undocumented.

Runtime impact

Order placement logic is missing CLOB constraints from the book response:

• min_order_size — placing an order below this threshold will be rejected by the exchange; PMXT currently has no way to read or enforce this constraint
• tick_size — prices not aligned to the tick increment are rejected; PMXT currently does not validate this
• neg_risk — on a neg_risk: true market, outcome pricing is inverted relative to a standard market; any code computing implied probability from prices will produce wrong values if unaware of this flag

Action needed

• Add asset_id, timestamp, hash, min_order_size, tick_size, neg_risk to the OrderBook schema in probable.yaml
• Type bids[] and asks[] elements as { price: string, size: string } in the spec
• Regenerate api.ts / ProbableRawOrderBook type
• Evaluate whether order-placement code in core/src/exchanges/probable/index.ts should read min_order_size and tick_size from a book fetch before submitting orders
• Evaluate neg_risk handling for any implied-probability computations