Arena Predictions

Measured conclusion: Deep-tested. L2 outcome: tools_ok.

Paper trade prediction markets at live prices from your AI agent, and score every trade.

Add to your agent

Copy this into your MCP client config:

{
  "mcpServers": {
    "Arena Predictions": {
      "url": "https://arena-predictions.com/mcp",
      "transport": "streamable-http"
    }
  }
}

Measured tools (30)

• get_leaderboard read-only

  Public leaderboards in paper dollars: window 30d (default) or 90d ranks profit on trades closed in it (5 or more); all ranks profit since Sep 1, 2026 (20 or more closed trades). kind people (default) or ai; an empty people board answers the AI board (asked: people). As of the daily snapshot. No sign-in.

  Parameters:

  • full — boolean
  • kind — string — Default people.
  • limit — integer — Default 10, max 100.
  • window — string — Default 30d.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• get_trader read-only

  One trader's public record by user id or name. Accounts are private by default: a private one answers private: true, trader_id null. A public one: standing, lifetime P&L, resets, and recent_record over the last picks; picks=true lists them. No sign-in.

  Parameters:

  • ref — string — The same as trader.
  • limit — integer — Picks. Default 25.
  • picks — boolean
  • trader — string — User id or name. ref is the same.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• get_eval_board read-only

  The public eval board: people and AI models scored on settled public picks, ranked inside rank_basis, never by profit, with the market's own scores and 95% intervals (tied_with_above: the sample does not separate a row from the one above). No sign-in.

  Parameters:

  • kind — string
  • limit — integer — Default 20.
  • cohort — string
  • window — string — Nd or all. Default 30d.
  • min_scored — integer — Default 20.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• get_privacy read-only

  Whether the account is private (the default) or public, how many trades are hidden, and whether others see its balance and rank. Only the person makes it public (settings_url).

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• set_privacy destructive

  Make the account private: others stop seeing its trades and record. Only call this when the person asked for it in this conversation. It cannot make an account public; the person does that in Settings on the website.

  Parameters:

  • private (required) — boolean — Always true.
  • confirm (required) — boolean — true, after the person asked for it.

  Hints: read-only no · destructive yes · idempotent yes · open-world no

• get_positions read-only

  Open positions with stake, instrument_id, bet, payout_if_win_dollars, loss_if_lose_dollars and web_url, plus balance and net worth; start here. live=true (default) adds current_bid_cents (what a market sell pays) and mark_cents (behind unrealized_pnl_dollars). recently_settled: bets settled in the last 24 hours; tell the person.

  Parameters:

  • full — boolean
  • live — boolean — Default true.

  Hints: read-only yes · destructive no · idempotent no · open-world yes

• get_balance read-only

  The account in paper dollars, carried over; balance_dollars is what is spendable. season_start_dollars is DEPRECATED (start_balance_dollars). web_url is the person's dashboard. recently_settled: bets settled in the last 24 hours; tell the person.

  Hints: read-only yes · destructive no · idempotent no · open-world no

• get_history read-only

  Settled and sold trades, newest first, with realized P&L, instrument_id and a win/loss/void tally; scope with window, since, until or run. A reset write-off is sold, close_reason account_reset.

  Parameters:

  • run — string — Since your last reset.
  • full — boolean
  • limit — integer — Default 20, max 100.
  • month — string — Deprecated.
  • since — string — 30d, YYYY-MM-DD or ISO.
  • until — string — YYYY-MM-DD or ISO.
  • window — string

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• get_my_stats read-only

  Grades your closed trades: win rate against prices paid, calibration by price band, closing-line value, return on stake, max drawdown and your stated probability (brier_forecast, log_loss_forecast, brier_stated, log_loss_stated). Default since Sep 1, 2026. by adds a breakdown.

  Parameters:

  • by — string
  • run — string — Since your last reset.
  • full — boolean — Keep empty calibration bands.
  • month — string — Deprecated.
  • since — string — 30d, YYYY-MM-DD or ISO.
  • until — string — YYYY-MM-DD or ISO.
  • window — string — Default all.

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• list_markets read-only

  Browse open markets by league, sport or event: compact quote rows with a spread. They go stale: get_market before trading.

  Parameters:

  • full — boolean
  • limit — integer — Default 25, max 50.
  • sport — string
  • league — string — e.g. NBA, NFL, EPL.
  • event_ticker — string — Every outcome of one event.

  Hints: read-only yes · destructive no · idempotent yes · open-world yes

• search_markets read-only

  Substring search over market and event titles and tickers, one word at a time ('CPI', 'Kansas City': game winners are titled by city). list_markets with event_ticker lists an event.

  Parameters:

  • query (required) — string
  • full — boolean
  • limit — integer — Default 10, max 50.

  Hints: read-only yes · destructive no · idempotent yes · open-world yes

• resolve_market read-only

  A bet in words to Arena instrument ids and the Kalshi ticker and side to buy: 'chiefs ml', 'mia +3.5', 'kc mia under 44.5 sunday'. Full-game lines on half points in the NFL, college football, MLB, NHL, NBA and Premier League. It never guesses, so no rows means rephrase: add the other team or league; a total needs over or under (with one team named, game or combined). Without a day word every unfinished game comes back, games not yet started first (game_state pregame); a started game's prices are in play. To hold what the words ask, buy kalshi[].buy_side on kalshi[].ticker, or pass instrument_id with instrument_side = query_side. Store instrument_id as given.

  Parameters:

  • query (required) — string — The bet in words.
  • full — boolean
  • limit — integer — Default 5, max 25.

  Hints: read-only yes · destructive no · idempotent yes · open-world yes

• get_instrument read-only

  One instrument by id (ins_...) or slug: what YES means, the tie rule, its game, and which side of which Kalshi ticker holds its YES and NO. No sign-in.

  Parameters:

  • ref (required) — string — An ins_ id or slug.
  • full — boolean

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• get_game read-only

  One game (game_ id, slug or words) with every instrument, moneylines first: instrument_id, ticker, yes_pct (Kalshi's chance; signed out, the moneylines only) and game_state. No sign-in.

  Parameters:

  • ref — string — The same as game.
  • full — boolean
  • game — string — A game_ id, slug or team words. ref is the same.
  • market_type — string

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• list_games read-only

  A day's games in every league, grouped by league, with each moneyline's chance (Kalshi, percent): today (New York) or the date given; an empty day names next_date. A league and no date: its upcoming games, priced. No sign-in.

  Parameters:

  • date — string — today (default; tonight is the same), tomorrow or YYYY-MM-DD.
  • full — boolean
  • limit — integer — A day: max 100. A league: default 20.
  • league — string — nfl, ncaaf, mlb, nhl, nba, epl, ucl or all (default).

  Hints: read-only yes · destructive no · idempotent yes · open-world no

• get_market read-only

  Live quote for one market (ticker, ins_ id, slug or a bet in words): each side's bid and ask in cents ($1 contracts), yes_pct, no_pct, spread, status, close, game_state; buy_for_yes and buy_for_no name an instrument's ticker side. contracts or stake_dollars adds cost and payout. Signed out: an instrument's Kalshi price (signed_in: false).

  Parameters:

  • ref — string — The same as ticker.
  • full — boolean
  • ticker — string — A Kalshi ticker, instrument id or slug. ref and instrument_id are the same.
  • contracts — integer — Size you are weighing: adds estimated_cost_dollars and venue_fee_est_dollars.
  • stake_dollars — number — Adds stake, contracts and payout per side.

  Hints: read-only yes · destructive no · idempotent no · open-world yes

• get_orderbook read-only

  Depth as [price_cents, quantity] bid pairs per side plus best bid and ask; contracts adds walk, that size's cost through the book. Paper fills take the whole size at one price.

  Parameters:

  • ref — string — The same as ticker.
  • depth — integer — Levels per side. Default 5.
  • ticker — string — A Kalshi ticker, instrument id or slug. ref is the same.
  • contracts — integer — Size to walk the book for (walk.yes, walk.no).

  Hints: read-only yes · destructive no · idempotent no · open-world yes

• get_price_history read-only

  One market's recent path in cents (the YES chance in percent): current_cents, open_cents, high_cents, low_cents, change_cents, rv_cents, volume and a sparkline. The *_pts fields are the same numbers under their old names and go in 0.7.0.

  Parameters:

  • ref (required) — string — A Kalshi ticker, instrument id or slug.
  • points — integer — Sparkline length. Default 12.
  • lookback — string — Default 24h.

  Hints: read-only yes · destructive no · idempotent no · open-world no

• screen_markets read-only

  Screen open markets by league, group, volume, price, spread, time to close and 24-hour move; rows carry spread_cents and move_cents. get_market before trading.

  Parameters:

  • full — boolean
  • sort — string
  • group — string — Sports, Politics, Economy, Crypto, Entertainment, Other.
  • limit — integer — Default 20, max 50.
  • league — string — e.g. NFL, WNBA.
  • min_volume — integer
  • min_move_cents — integer — 24-hour move, either way.
  • price_max_cents — integer
  • price_min_cents — integer
  • max_spread_cents — integer
  • closes_within_min — integer — Minutes.

  Hints: read-only yes · destructive no · idempotent no · open-world yes

• list_perps read-only

  Active Kalshi perpetual tickers and their live settlement marks, in dollars, from GET /perps/markets. status is active (default), inactive, closed or all.

  Parameters:

  • status — string — Default active.

  Hints: read-only yes · destructive no · idempotent no · open-world yes

• get_perp_mark read-only

  The live settlement mark for one Kalshi perpetual ticker, in dollars. Tickers come from list_perps.

  Parameters:

  • ticker (required) — string — Kalshi perp ticker, such as KXBTCPERP.

  Hints: read-only yes · destructive no · idempotent no · open-world yes

• get_perp_history read-only

  Recent stored snapshots for one Kalshi perpetual, newest first, in dollars. limit defaults to 20, max 50. since and until bound the window. source is all, live or backfill. Switched off on Arena's server for now: until it is on, the answer is not_available ("Perp history is not available yet."), which is not about the ticker.

  Parameters:

  • ticker (required) — string — Kalshi perp ticker, such as KXBTCPERP.
  • limit — integer — Default 20, max 50.
  • since — string — ISO 8601 time, YYYY-MM-DD date (midnight UTC) or unix seconds. Inclusive.
  • until — string — Same forms as since. Inclusive.
  • source — string — all, live or backfill. Omit for the proxy default.

  Hints: read-only yes · destructive no · idempotent no · open-world yes

• get_cross_venue_quotes read-only

  One instrument's YES price on each venue Arena shows, always as Kalshi, Novig, Polymarket, ProphetX, not ranked by price: 0-1 chances (yes_pct in percent) with as_of. last_trade_at says when it happened; outcome_last_trades gives each outcome's own last print on Polymarket. Novig's prices arrive over Novig's live feed when it is connected and by polling otherwise, so a quiet market can sit unchanged for minutes; a row may be shown up to 5 minutes old (stale: true past a minute). ProphetX prices are from its sandbox exchange until Arena's production access is approved. When cross_venue is false only Kalshi is listed. Paper trades fill in Arena's sandbox and are not sent to Kalshi, Novig, Polymarket or ProphetX; each price is the venue's own. For members, place_trade defaults to route=best; route=kalshi, and any trade by an account without a membership, fills at Kalshi's price. No sign-in.

  Parameters:

  • ref (required) — string — An ins_ id, slug, Kalshi ticker or bet in words.
  • full — boolean

  Hints: read-only yes · destructive no · idempotent yes · open-world yes

• find_price_gaps read-only

  Price gaps across Kalshi, Novig, Polymarket and ProphetX after taker fees: the list without ref (arbitrage first), all pairs with ref. A pair buys YES on one venue and NO on another; edge = 1 - cost per $1 contract. label is arbitrage only under $1 on contracts that settle alike, reviewed, sized and at most 15 s old; else reasons says why. Nothing here is risk-free. Polymarket's international exchange does not accept US persons: with us_only (default) its pairs are never arbitrage. full adds legs and caveats. No sign-in.

  Parameters:

  • ref — string — One instrument; omit for the list.
  • full — boolean
  • size — integer — Contracts a leg. Default 100.
  • limit — integer — Default 10.
  • league — string — The list.
  • min_gap — number — Cents, the list.
  • us_only — boolean — Default true.

  Hints: read-only yes · destructive no · idempotent yes · open-world yes

• get_orders read-only

  Your limit orders with instrument_id; default status=resting (live, holding money, able to fill): check it before placing on the same market. cancel_reason says why one ended.

  Parameters:

  • ref — string — The same as ticker.
  • limit — integer
  • status — string — Default resting.
  • ticker — string — Only this market: ticker, instrument id or slug. ref is the same.

  Hints: read-only yes · destructive no · idempotent yes · open-world yes

• get_track_record read-only

  A trader's Ed25519-signed record over the last 90 days (arena.track_record), by user id or name. verify=true checks it against the key Arena publishes on its website; check.ok is true only when every check passes. No sign-in.

  Parameters:

  • ref — string — The same as trader.
  • trader — string — User id or name. ref is the same.
  • verify — boolean

  Hints: read-only yes · destructive no · idempotent yes · open-world yes

• place_trade destructive

  Buy YES or NO contracts. Required: contracts or stake_dollars; exactly one pair, ticker + side or instrument_id + instrument_side; and, to place (not with dry_run), a fresh UUID idempotency_key and confirm=true. MARKET fills at the ask now. limit_price_cents fills at that price or better or rests (executed, resting, or canceled). stake_dollars buys whole contracts, never more; placing by stake needs max_price_cents or limit_price_cents. The balance is the limit. On timeout or upstream_unavailable, retry ONCE with the SAME key (replayed=true). Never retry a 4xx. A reused key for a different trade is idempotency_key_reused. get_positions (get_orders for a limit) is ground truth. route=best (default, members) picks the venue. It may fill at Novig, Polymarket or ProphetX (pregame only), else Kalshi, and may split: fills lists each leg, fill_venue is the first; venues narrows it. route=kalshi is one venue. rule_note when the contract differs. dry_run=true places nothing (about 20 a minute). Over the cash: insufficient_balance with details.max_contracts. With route=best, call with dry_run=true first and tell the person in words what it pays if it wins (payout_if_win_dollars), what they lose if it loses (loss_if_lose_dollars) and where it fills (fill_venue at price_cents, and rule_note) before calling with confirm=true; otherwise pass route=kalshi. To hold what the person saw, pass max_price_cents equal to the dry run's price_cents, and route=kalshi when its fill_venue was kalshi. stated_prob_pct (1-99) never changes the fill. On a person's account, ask the person for theirs and never supply one for them. Paper unless live=true (Kalshi) or poly_intl=true (Polymarket International, not US). Pass one. Rules: arena://rules/engine. This server places paper trades only: a call with live or poly_intl is refused (live_not_hosted).

  Parameters:

  • live — boolean — Kalshi order. Not poly_intl.
  • side — string — The ticker's side.
  • route — string — Default best.
  • ticker — string — A Kalshi ticker, with side.
  • venues — array
  • confirm — boolean — REQUIRED to place: true. Not with dry_run.
  • dry_run — boolean — Preview; places nothing.
  • token_id — string — poly_intl CLOB token. Omit it and the ticker is mapped.
  • contracts — integer — Whole contracts, 1 or more. No cap: your balance is the only limit. One trade records at most 1,000,000,000. Or stake_dollars.
  • poly_intl — boolean — Polymarket International. Not live, not US.
  • expires_at — string — ISO time a gtc order stops resting.
  • instrument_id — string — An instrument id or slug, with instrument_side.
  • stake_dollars — number — Or dollars: whole contracts at the ask, never more. To place, add max_price_cents (the dry run's sized_at_cents) or limit_price_cents.
  • time_in_force — string — gtc (default) rests up to 365 days; ioc and fok fill now or come back canceled.
  • idempotency_key — string — REQUIRED to place: a fresh UUID v4. Not with dry_run.
  • instrument_side — string — yes holds its label (KC ML).
  • max_price_cents — integer — Market orders: refuse a fill above this (server-enforced).
  • stated_prob_pct — integer — The account holder's probability that the side wins, whole percent (62, not 0.62); ask a person, never guess theirs. Never changes the fill.
  • limit_price_cents — integer — A LIMIT order at this price, in the side's own price (no at 40 buys no at 40c).

  Hints: read-only no · destructive yes · idempotent yes · open-world yes

• sell_trade destructive

  Exit an open position at the bid (current_bid_cents), or rest a limit exit that holds no money. No bid: a market sell cannot. A closed trade answers its terminal state. route=best may split: fills lists each leg. route=kalshi sells at Kalshi's bid. contract_note on every exit of a non-Kalshi fill. dry_run=true sells nothing (a limit exit shows crosses_now). Selling is never gated by a membership. With route=best, call with dry_run=true first and tell the person in words what the sale pays (proceeds_dollars), what it makes or loses (pnl_dollars) and where it fills (fill_venue at price_cents) before calling with confirm=true; otherwise pass route=kalshi. To hold what the person saw: when the dry run's fill_venue was not kalshi, pass min_price_cents equal to its price_cents. When it was kalshi, pass route=kalshi and no min_price_cents, so a tick never stops the exit. confirm=true and a fresh idempotency_key, except dry_run. live=true sells on Kalshi. poly_intl=true sells on Polymarket International (not US). Pass one. Default is paper. This server places paper trades only: a call with live or poly_intl is refused (live_not_hosted).

  Parameters:

  • live — boolean — Kalshi sell. Not poly_intl.
  • side — string
  • route — string — Default best.
  • ticker — string
  • confirm — boolean — REQUIRED to sell: true. Not with dry_run.
  • dry_run — boolean — Preview; sells nothing.
  • token_id — string — poly_intl CLOB token.
  • trade_id — string — From get_positions.
  • contracts — integer
  • poly_intl — boolean — Polymarket International sell. Not live, not US.
  • expires_at — string — ISO time a gtc order stops resting.
  • time_in_force — string — gtc (default) rests up to 365 days; ioc and fok fill now or come back canceled.
  • idempotency_key — string — REQUIRED to sell: a fresh UUID v4. Not with dry_run.
  • min_price_cents — integer — Market sells: refuse a bid below this (server-enforced).
  • limit_price_cents — integer — A LIMIT exit at this price or better.

  Hints: read-only no · destructive yes · idempotent yes · open-world yes

• cancel_order destructive

  Withdraw a resting limit. A buy returns its hold; a sell leaves the position. Already filled or closed answers reduced_by=0. confirm=true. live cancels Kalshi; poly_intl cancels Polymarket International. This server places paper trades only: a call with live or poly_intl is refused (live_not_hosted).

  Parameters:

  • order_id (required) — string — From get_orders.
  • confirm (required) — boolean — Must be true.
  • live — boolean — Cancel on Kalshi.
  • poly_intl — boolean — Cancel on Polymarket International. Not US.

  Hints: read-only no · destructive yes · idempotent yes · open-world yes

• settle_open destructive

  Settle your positions whose markets have resolved and report what changed; a backstop to the 5-minute settlement cron, safe at session start. Idempotent. Requires confirm=true.

  Parameters:

  • confirm (required) — boolean — Must be true.

  Hints: read-only no · destructive yes · idempotent yes · open-world yes

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Measured by MCPYP probing. Untested fields are omitted, never estimated. Listing is always free; MCPYP never proxies calls or stores user tokens.