Coin Railz Prediction Markets API

openapi: 3.2.0
info:
  title: Coin Railz Agent Payment Prediction Markets API
  version: 3.0.0
  description: Production-grade x402 micropayment infrastructure for AI agents.
  contact:
    email: support@coinrailz.com
    url: https://coinrailz.com
  x-guidance: 'Use Coin Railz when an agent needs paid, structured financial or operational data without creating an account or API key. Choose the operation by its summary, description, tags, input schema, and x-price-usd. Useful starting points include first-call for a low-cost payment test; token-metadata, gas-price-oracle, wallet-risk, approval-manager, and transaction-builder for transaction preparation; compliance-check for informational risk screening; prediction-market-odds for market research; and solana-yield-finder for yield discovery.


    For a paid call, send the exact documented HTTP method, URL, content type, and JSON body without a payment header. The service returns HTTP 402 with x402Version 2 and an accepts array. Select one complete offer your wallet supports. Circle Agent Wallet and Gateway clients should prefer the eip155:5042 Arc Mainnet offer when available; Base clients can select eip155:8453. Preserve the selected offer exactly, including scheme, network, asset, amount, payTo, facilitator, resource, and any extra metadata. Sign that authorization with an x402 v2-compatible client, then retry the identical request with PAYMENT-SIGNATURE. X-PAYMENT remains available for compatible legacy clients. Do not send a standalone token transfer or construct a transaction-hash wrapper from this guidance.


    Validate required fields and constraints from each operation''s request schema before authorizing payment. Treat risk, compliance, market, yield, and investment outputs as informational analysis rather than legal, banking, or investment advice. Prices are per call and the live 402 challenge is authoritative. Responses are JSON unless the operation states otherwise.'
  x-payment-info:
    protocol: x402
    x402Version: 2
    network: eip155:8453
    asset: USDC
    assetAddress: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913'
    recipientWallet: '0xa4bbe37f9a6ae2dc36a607b91eb148c0ae163c91'
    facilitator: https://api.cdp.coinbase.com/platform/v2/x402
    supportedNetworks:
    - network: eip155:8453
      asset: USDC
      assetAddress: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913'
      facilitator: https://api.cdp.coinbase.com/platform/v2/x402
    - network: eip155:5042
      asset: USDC
      assetAddress: '0x3600000000000000000000000000000000000000'
      gatewayVerifier: '0x77777777Dcc4d5A8B6E418Fd04D8997ef11000eE'
      facilitator: https://gateway-api.circle.com
  x-payment-manifest: https://coinrailz.com/x402/payment-manifest.json
servers:
- url: https://coinrailz.com
  description: Current environment
- url: https://coinrailz.com
  description: Production
security:
- apiKey: []
tags:
- name: Prediction Markets
  description: Polymarket, Kalshi, and prediction data
paths:
  /x402/polymarket-events:
    post:
      tags:
      - Prediction Markets
      summary: Polymarket Events
      description: Trending Polymarket prediction market events with current yes/no prices, volume, and liquidity across politics, crypto, sports, and science.
      x-price-usd: 0.25
      operationId: polymarketEvents
      requestBody:
        content:
          application/json:
            schema:
              type: object
              properties:
                category:
                  type: string
                limit:
                  type: integer
                  default: 10
      responses:
        '200':
          description: Trending prediction markets
        '402':
          description: Payment Required
      x-featured: false
  /x402/polymarket-odds:
    post:
      tags:
      - Prediction Markets
      summary: Polymarket Odds
      description: Current odds and price history for a specific Polymarket event. Returns yes/no bid/ask, 24h volume, and last trade timestamp.
      x-price-usd: 0.5
      operationId: polymarketOdds
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
              - eventId
              properties:
                eventId:
                  type: string
      responses:
        '200':
          description: Event odds and volume
        '402':
          description: Payment Required
      x-featured: false
  /x402/polymarket-search:
    post:
      tags:
      - Prediction Markets
      summary: Polymarket Search
      description: Search Polymarket prediction markets by keyword or topic. Returns matching events with current prices, volume, and market close date.
      x-price-usd: 0.25
      operationId: polymarketSearch
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
              - query
              properties:
                query:
                  type: string
                limit:
                  type: integer
                  default: 10
      responses:
        '200':
          description: Search results
        '402':
          description: Payment Required
      x-featured: false
  /x402/prediction-market-odds:
    post:
      tags:
      - Prediction Markets
      summary: Prediction Market Odds
      description: Aggregated prediction market odds from Polymarket and Kalshi for any topic. Returns consensus probability with per-platform breakdown and total volume.
      x-price-usd: 0.5
      operationId: predictionMarketOdds
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
              - topic
              properties:
                topic:
                  type: string
                platforms:
                  type: array
                  items:
                    type: string
      responses:
        '200':
          description: Aggregated odds
        '402':
          description: Payment Required
      x-featured: false
  /x402/kalshi-markets:
    post:
      tags:
      - Prediction Markets
      summary: Kalshi Markets
      description: Active markets from Kalshi, a CFTC-regulated prediction exchange. Returns yes/no ask prices, volume, and open interest. Filter by category or keyword.
      x-price-usd: 0.25
      operationId: kalshiMarkets
      requestBody:
        content:
          application/json:
            schema:
              type: object
              properties:
                limit:
                  type: integer
                  default: 20
                category:
                  type: string
      responses:
        '200':
          description: Active Kalshi markets
        '402':
          description: Payment Required
      x-featured: false
  /x402/kalshi-odds:
    post:
      tags:
      - Prediction Markets
      summary: Kalshi Odds
      description: Current yes/no prices and orderbook depth for a specific Kalshi market. Returns bid/ask spread, last price, volume, and open interest for CFTC-regulated event contracts.
      x-price-usd: 0.5
      operationId: kalshiOdds
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
              - marketId
              properties:
                marketId:
                  type: string
                  description: Kalshi market ticker ID
      responses:
        '200':
          description: Kalshi market odds and orderbook
        '402':
          description: Payment Required
      x-featured: false
  /x402/kalshi-search:
    post:
      tags:
      - Prediction Markets
      summary: Kalshi Search
      description: Search Kalshi prediction markets by keyword or event type. Returns matching CFTC-regulated markets with current yes prices, volume, and expiration dates.
      x-price-usd: 0.25
      operationId: kalshiSearch
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
              - query
              properties:
                query:
                  type: string
                limit:
                  type: integer
                  default: 10
      responses:
        '200':
          description: Kalshi search results
        '402':
          description: Payment Required
      x-featured: false
  /x402/prediction-market-spread:
    post:
      tags:
      - Prediction Markets
      summary: Prediction Market Cross-Platform Spread
      description: 'Live cross-platform spread analysis: Polymarket vs Kalshi for identical real-world events. Returns YES probability divergence, arbitrage opportunity ranking by spread magnitude, matchConfidence, actionHint, and edgeBps per opportunity.'
      x-price-usd: 0.25
      x-featured: true
      operationId: predictionMarketSpread
      requestBody:
        content:
          application/json:
            schema:
              type: object
              properties:
                limit:
                  type: integer
                  default: 10
                  description: Max opportunities to return (1-25)
                minSpreadPct:
                  type: number
                  default: 0
                  description: Minimum spread in percentage points (e.g. 3 filters out spreads below 3pp)
                minConfidence:
                  type: string
                  enum:
                  - low
                  - medium
                  - high
                  description: Minimum match confidence tier to include
      responses:
        '200':
          description: Cross-platform spread opportunities ranked by magnitude
        '402':
          description: Payment Required
components:
  securitySchemes:
    apiKey:
      type: apiKey
      in: header
      name: X-API-KEY
      description: Prepaid credits API key (cr_live_...). Obtain via GET /api/m2m/credits/trial (free $5) or POST /api/m2m/credits/checkout/session (paid).
    bearerApiKey:
      type: http
      scheme: bearer
      description: 'Same cr_live_ key as X-API-KEY, passed as Authorization: Bearer <key>.'
    x402:
      type: apiKey
      in: header
      name: X-PAYMENT
      description: x402 protocol on-chain USDC payment. Base64url-encoded signed payment payload. See /.well-known/x402.json for facilitator details.
    mpp:
      type: http
      scheme: payment
      description: 'MPP (Machine Payments Protocol) credential. Authorization: Payment <base64-credential>. See /.well-known/mpp.json.'
externalDocs:
  description: Full x402 service catalog
  url: https://coinrailz.com/x402/catalog