MassPredict API

Access aggregated prediction market data from Polymarket, Kalshi, Manifold, PredictIt, ForecastEx, Futuur, Limitless, and SwiPredict through a single unified API. Real-time prices, historical data, and arbitrage detection.

Base URL

https://api.masspredict.ai/v1

Quick Example

curl -X GET "https://api.masspredict.ai/v1/search?q=bitcoin" \
  -H "Authorization: Bearer YOUR_API_KEY"

Authentication

All API requests require authentication using a Bearer token. Include your API key in the Authorization header:

Authorization: Bearer YOUR_API_KEY

Get your API key from your dashboard after signing up for a plan.

Rate Limits

Rate limits depend on your plan:

• Free: 100 requests/day
• Pro: 10,000 requests/day
• Enterprise: Unlimited

Rate limit headers are included in every response:

X-RateLimit-Limit: 10000
X-RateLimit-Remaining: 9847
X-RateLimit-Reset: 1704067200

Search Markets

Search across all supported prediction markets.

GET /v1/search

Parameters

Response

{
  "markets": [
    {
      "id": "mp_btc_150k_2025",
      "title": "Will Bitcoin reach $150K by end of 2025?",
      "category": "crypto",
      "average_yes": 42.3,
      "platforms": [
        {
          "name": "polymarket",
          "yes_price": 45,
          "volume": 12400000,
          "url": "https://polymarket.com/..."
        },
        {
          "name": "kalshi",
          "yes_price": 38,
          "volume": 2100000,
          "url": "https://kalshi.com/..."
        }
      ],
      "spread": 7,
      "total_volume": 14500000,
      "end_date": "2025-12-31T23:59:59Z"
    }
  ],
  "total": 847,
  "offset": 0,
  "limit": 20
}

Get Market Details

Get detailed information about a specific market.

GET /v1/markets/{market_id}

Price History

Get historical price data for a market.

GET /v1/markets/{market_id}/history

Parameters

Response

{
  "market_id": "mp_btc_150k_2025",
  "interval": "1d",
  "history": [
    {
      "timestamp": "2024-12-01T00:00:00Z",
      "prices": {
        "polymarket": 41,
        "kalshi": 38,
        "average": 39.5
      },
      "volume": 1240000
    }
  ]
}

Arbitrage Opportunities

Get current arbitrage opportunities across platforms.

GET /v1/arbitrage

Parameters

Accuracy Data

Get platform accuracy statistics and resolved market data.

GET /v1/accuracy

{
  "rankings": [
    {
      "platform": "kalshi",
      "accuracy": 87.3,
      "brier_score": 0.127,
      "resolved_markets": 1247
    },
    {
      "platform": "polymarket",
      "accuracy": 84.1,
      "brier_score": 0.159,
      "resolved_markets": 892
    }
  ],
  "by_category": {
    "politics": [...],
    "crypto": [...]
  }
}

Webhooks

Subscribe to real-time updates for price changes and arbitrage opportunities.

POST /v1/webhooks

{
  "url": "https://your-server.com/webhook",
  "events": ["arbitrage.detected", "price.change"],
  "filters": {
    "min_spread": 5,
    "categories": ["crypto", "politics"]
  }
}

MCP — Connect Agents

The MassPredict MCP server lets Claude, Cursor, and any other MCP-compatible agent query market intelligence and submit paper trades directly. JSON-RPC 2.0, protocol version 2024-11-05.

https://masspredict.ai/.netlify/functions/masspredict-mcp

Authentication

Bearer token from the same agent_api_keys table the REST endpoints use. Pass Authorization: Bearer <key> on every request. Per-agent rate limits and SP wallet shared across both surfaces.

Tools (6 live · 1 deferred)

• search_markets — tokenized search across all cross-platform markets, with client-side reranking by relevance
• get_market_intelligence — full market detail (prices, volume, recent news, similar markets) for a single market
• compare_platforms — paired cross-platform-match output showing price spreads between Kalshi / Polymarket / etc.
• get_resolution_history — past resolution accuracy and outcomes by market category
• get_my_paper_portfolio — calling agent's paper-trade positions, P/L, and SP balance
• submit_paper_trade — execute a paper trade on the agent's behalf (writes to raven_sim_trades)
• get_predictapedia_entry — DEFERRED v0.1. Tool is registered; handler returns a not-yet-implemented stub.

Claude Desktop config

Add to your claude_desktop_config.json:

{
  "mcpServers": {
    "masspredict": {
      "url": "https://masspredict.ai/.netlify/functions/masspredict-mcp",
      "headers": {
        "Authorization": "Bearer YOUR_AGENT_API_KEY"
      }
    }
  }
}

Restart Claude Desktop and the six live tools appear under masspredict. Same rate limits and SP wallet model as the REST endpoints above.

API Pricing

Choose the plan that fits your needs.