Esports momentum API: bet the book that has not moved yet
Updated · Published
Quick answer: GET /v7/{sport}/momentum returns first-mover +EV plays: one book moved first, its new two-way price devigs to a fair, and the play is a lag book still offering the old price. Filter by kind (all, line, prop), market, book (lag book), mover (first mover), min_ev and window_minutes. Builder ($99/mo) and up.
| Piece of a play | Field | What it tells you |
|---|---|---|
| Who moved first | move.book, move.from_*, move.to_*, move.moved_at | The mover and the size of the move |
| What fair is | fair.decimal, fair.probability, fair.source | The mover's two-way devigged, mover_devig |
| Where to bet | bet.book, bet.price_decimal, bet.deeplink | The best stale price still offered |
| How good it is | bet.ev_pct, bet.gap_pts, bet.behind_seconds | EV vs fair, the implied gap, how stale it is |
| Who else is late | stale_books | Every lag book still beating fair, ranked by EV |
The mechanic: the first mover is the truth
When a number is wrong, one book usually moves first. Momentum treats that book's new two-way price as the truth, not the consensus: devig the mover's pair and you get a fair probability the rest of the market has not caught up to. A play exists when a lag book still offers a price that beats that fair.
Both surfaces run the same way. On lines, the per-book shift tape supplies the move and the live board supplies the lag prices. On props, a quote that just changed is the move and the still-current quotes on the same market across other books are the lag candidates. If there is no devig-able pair on the mover or no open lag book, there is no play, just tape.
Anatomy of a play
Each play is one row with four parts. The move block records which book moved first: the book key, the from and to prices in american and decimal, when it moved, the implied move in points, and any other_movers that followed. The fair block is the mover's new two-way devigged: american, decimal, probability, with source: mover_devig so you know whose number set fair.
The bet block is the trade: which lag book still offers a beating-fair price, that price in american and decimal, the ev_pct against fair, the gap_pts between the offered implied chance and fair, how many behind_seconds the price has sat, and the deeplink to the offer. stale_books lists every lag book still beating fair, each with its own EV and observed_at, sorted best first, so if the top price is gone the second-best is already ranked.
| Block | Fields | Read it as |
|---|---|---|
move | book, from_american, to_american, from_decimal, to_decimal, moved_at, move_pct, other_movers | Pinnacle moved TYLOO first, Betway followed |
fair | american, decimal, probability, source | The mover's pair devigged, e.g. 60% fair |
bet | book, price_american, price_decimal, ev_pct, gap_pts, behind_seconds, deeplink | A lag book still hangs +EV price |
stale_books | book, decimal, american, ev_pct, observed_at | Every other book still behind, ranked |
Filter the board to your strategy
| Param | Values | Effect |
|---|---|---|
kind | all (default), line, prop | Team lines, player props, or both |
market | Registry market key or stat type | One market only, e.g. total_rounds |
book | Book key | Only plays bettable at that lag book |
mover | Book key | Only plays where that book moved first |
min_ev | Percent, e.g. 3 | Floor on bet.ev_pct |
window_minutes | 5-360, default 60 | How far back a move counts |
Line plays moving in the last 30 minutes, 3%+ EV
curl -s -H "X-API-Key: $KASHROCK_API_KEY" \ "https://kashrock.up.railway.app/v7/cs2/momentum?kind=line&min_ev=3&window_minutes=30"
Size the play with the math tools
Two helpers do the arithmetic the same way the published SDK does, no plan required. GET /v7/tools/convert takes one price spelling (american, decimal, probability or percent) and returns all of them. GET /v7/tools/kelly takes your fair probability and the offered price and returns the Kelly stake, quarter-Kelly by default. Real responses:
Convert a price, then size it
curl -s -H "X-API-Key: $KASHROCK_API_KEY" \
"https://kashrock.up.railway.app/v7/tools/convert?american=125"
# {"american":125.0,"decimal":2.25,"probability":0.444444,"percent":44.44}
curl -s -H "X-API-Key: $KASHROCK_API_KEY" \
"https://kashrock.up.railway.app/v7/tools/kelly?fair_probability=0.5&decimal=2.25&bankroll=1000"
# {"fair_probability":0.5,"decimal":2.25,"kelly_full_pct":10.0,
# "kelly_fraction":0.25,"stake_pct":2.5,"ev_pct":12.5,"stake_amount":25.0}Use the play's own fair.probability as the input and the sizing stays honest to the same fair the endpoint priced. The parlay post explains why leg fair always excludes the leg's own book, the same idea momentum applies to a single price.
Momentum vs flow: detector vs pricer
GET /v7/{sport}/flow tells you a move happened: steam, shift, volume and whale plays with the thresholds they cleared. GET /v7/{sport}/momentum prices what the move left behind: which books still offer the old number and how much EV that price carries. Flow answers "did it move", momentum answers "where is it still cheap".
Momentum is a Builder ($99/mo) endpoint; the math tools need only a key. More books on the board means more lag prices, which is why the two sportsbooks that went live today matter here: the BigBola and Strendus post covers them, and the odds movement page is the flow reference.
FAQ
What is a first-mover play?
One book moved a price first, its new two-way devigs to a fair, and a lag book still offers the old price. The play is the lag book's price beating that fair, with the EV stated on the response.
How is momentum different from flow?
Flow detects that a move happened (steam, shift, volume, whale) and reports the thresholds it cleared. Momentum prices the lag: which books still hang the old number and the EV vs the mover's devigged fair.
What is fair in a momentum play?
The first mover's new two-way price, devigged. The fair block carries american, decimal and probability with source mover_devig, so the edge is measured against the book that actually moved, not a blended consensus.
What does stale_books mean?
Every lag book still offering a price that beats the mover's fair, each with its own decimal, american, ev_pct and observed_at. bet is the best of them; the rest are alternates if the top price is gone.
Which plan do I need for momentum?
Builder ($99/mo) and up. The math helpers, GET /v7/tools/convert and GET /v7/tools/kelly, need only an API key.
