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Three x402 endpoints for US-regulated prediction-market intelligence. Kalshi’s REST API is fully public — but the value here is in the derivation: slopes, cross-source JOINs, and momentum-vs-market signals an agent would otherwise have to compute itself.

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What you get

EndpointCostReturns
POST /kalshi/consensus-trend$0.05Slope-per-hour over 24h + 3d, acceleration signal, volatility band, days-to-resolve — derived from Kalshi’s unique forecast_history
POST /kalshi-polymarket/spread$0.05Cross-source spread between Kalshi and Polymarket on the same topic, with arbitrage direction. JOIN that single-source passthrough APIs structurally can’t return
POST /kalshi/sports-live-edge$0.05Play-by-play momentum vs market candle reaction → latency-arb signal for live Football / Basketball / Soccer / Hockey / Baseball / WNBA markets
Per-call payment in USDC on Base via x402. No subscription, no API key, no free tier.

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Why derived over raw

Kalshi exposes ~50 public no-auth endpoints across 10,821 series (Entertainment 2,445 · Sports 2,172 · Politics 1,986 · Elections 1,404 · Economics 563 · Financials 516 · …). An agent can read them directly — but every consuming agent then re-implements the same math:
  • Fit a slope through forecast_history points to detect regime change
  • Match Kalshi events against Polymarket equivalents by keyword + price proximity
  • Compute momentum from play-by-play events and compare to market reaction lag
Graph Advocate does it once, exposes the answer. The cross-source /spread endpoint in particular is the defensible play: passthrough APIs return one source at a time and can’t JOIN — so the cross-venue arbitrage signal stays valuable even as more upstream sources come online.

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Sample: consensus trend for an event

curl -X POST 'https://graphadvocate.com/kalshi/consensus-trend' \
  -H 'Content-Type: application/json' \
  -d '{"event": "KXELONMARS-99"}'
Response (truncated): 
{
  "kalshi_event_ticker": "KXELONMARS-99",
  "event_title": "Will Elon Musk visit Mars in his lifetime?",
  "category": "World",
  "consensus_probability_now": 0.18,
  "slope_per_hour_24h": -0.0004,
  "slope_per_hour_3d": -0.0001,
  "acceleration_signal": -0.0003,
  "interpretation": "accelerating-down",
  "volatility_24h_stdev": 0.012,
  "days_to_resolve": 3287.4,
  "markets_in_event": 1,
  "history_points_analyzed": 142,
  "kalshi_source": "https://api.elections.kalshi.com/trade-api/v2/events/KXELONMARS-99/forecast_history",
  "agent_note": "Forecast history is Kalshi's published consensus probability over time. Use slope+acceleration to detect regime changes before they're priced in. Pair with /kalshi-polymarket/spread for cross-source arbitrage."
}
How to use it. A positive acceleration_signal means the slope is steepening upward — the market is converging on YES faster than it was 3 days ago. Negative means the opposite. interpretation collapses the signal into one of accelerating-up, accelerating-down, stable, or insufficient-history so an agent can branch without parsing.

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Sample: cross-source spread

curl -X POST 'https://graphadvocate.com/kalshi-polymarket/spread' \
  -H 'Content-Type: application/json' \
  -d '{"topic": "fed rate", "limit": 5}'
Response: 
{
  "topic_keyword": "fed rate",
  "kalshi_candidates": 3,
  "polymarket_candidates": 2,
  "pairs": [
    {
      "kalshi_ticker": "KXFED-25DEC-CUT25",
      "kalshi_yes_mid": 0.62,
      "polymarket_market_slug": "fed-rate-cut-december",
      "polymarket_yes_mid": 0.58,
      "spread_yes_kalshi_minus_poly": 0.04,
      "spread_bps": 400,
      "arbitrage_direction": "long-poly-short-kalshi"
    }
  ],
  "agent_note": "Spread > 200bps in either direction is a candidate arbitrage; verify the two markets actually resolve on the same condition before sizing. Cross-source data single-source APIs can't return in one call.",
  "sources": {
    "kalshi": "https://api.elections.kalshi.com/trade-api/v2",
    "polymarket": "token-api proxy"
  }
}
Important: the pairing uses keyword overlap + price-proximity scoring. You must verify the two markets actually resolve on the same on-chain condition before sizing — otherwise the “arbitrage” is just basis risk.

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Sample: live sports edge

curl -X POST 'https://graphadvocate.com/kalshi/sports-live-edge' \
  -H 'Content-Type: application/json' \
  -d '{
    "milestone": "<kalshi-sports-milestone-id>",
    "market": "<optional-kalshi-market-ticker>"
  }'
The milestone is Kalshi’s identifier for a specific live game; market is an optional ticker for the market whose candlesticks you want compared against the play-by-play. Response includes momentum_score_last_5_events, market_reaction_pct_last_hour, and a latency_arbitrage_signal of one of upside-lag-likely, downside-lag-likely, market-tracking-stats, or null (insufficient data). How to use it. When momentum_score is strongly one-way (≥0.6 or ≤0.2) but market_reaction_pct is near zero, the market hasn’t fully priced the play-by-play yet — latency-arb window. Verify orderbook depth before sizing — low liquidity will eat the edge.

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How it differs from /polymarket/* and /hyperliquid/*

These three Kalshi endpoints are derived signals on top of a fully public upstream — different model than the polymarket/hyperliquid trader-intelligence endpoints which proxy through gated data sources. Kalshi’s API is free for anyone to read; Graph Advocate’s value here is in the math:
  • /polymarket/risk — wallet-type detection (binary signal from on-chain probe)
  • /hyperliquid/risk — liquidation rate + funding burn (derived from per-trade ledger)
  • /kalshi/consensus-trend — slope of Kalshi’s unique forecast percentile history
  • /kalshi-polymarket/spread — JOIN that no single-source API can return
  • /kalshi/sports-live-edge — momentum-vs-market reaction lag
If you want to inspect the routing for free, send a plain-English question to POST / (A2A JSON-RPC) and Graph Advocate will name the right kalshi/* endpoint and hand back the exact paid curl — without charging.

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Source

kalshi.py — the three derivation functions and how they fetch from Kalshi’s public REST and Polymarket data sources.