MassPredict API
Access aggregated prediction market data from Polymarket, Kalshi, PredictIt, Manifold, Metaculus, Smarkets, Futuur, and Limitless 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
| Parameter | Type | Description |
|---|---|---|
| q required | string | Search query |
| platforms | string[] | Filter by platforms: polymarket, kalshi, predictit, manifold, metaculus |
| category | string | Filter by category: politics, crypto, economics, sports, tech, science |
| limit | integer | Results per page (default: 20, max: 100) |
| offset | integer | Pagination offset |
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
| Parameter | Type | Description |
|---|---|---|
| interval | string | Data interval: 1h, 1d, 1w (default: 1d) |
| start | ISO 8601 | Start date |
| end | ISO 8601 | End date |
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
| Parameter | Type | Description |
|---|---|---|
| min_spread | number | Minimum spread % (default: 3) |
| min_volume | number | Minimum combined volume |
Accuracy Data
Get platform accuracy statistics and resolved market data.
GET /v1/accuracy
{
"rankings": [
{
"platform": "metaculus",
"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"]
}
}
API Pricing
Choose the plan that fits your needs.
- 10,000 requests/day
- All endpoints
- Historical data
- Webhooks
- Email support
- Unlimited requests
- Dedicated infrastructure
- Custom integrations
- SLA guarantee
- Priority support