Step 1 — Get an API key
Sign up at dashboard.predexon.com
No credit card required. The free plan gives you 1,000 requests/month against the entire Data API — enough to evaluate everything.Open dashboard →
Copy your keys
The dashboard issues two separate keys — one for market data, one for trading. Both go in the
x-api-key header of their respective requests.| Key | Used against | Surfaces |
|---|---|---|
| Data API key | api.predexon.com, wss.predexon.com | Data API, WebSocket, MCP server |
| Trading API key | trade.predexon.com | Trading API (accounts, orders, transfers, fees) |
A Data API key will be rejected by
trade.predexon.com and vice versa. If you see 401 / 403, double-check which key you’re sending.Step 2 — Make your first call
This call lists the top 5 trending markets on Polymarket. It works on the free plan with no setup.Step 3 — Pick your path
Now go to the guide for what you’re building.Quant / data trader
Backtest with orderbook history, build smart-money models, stream live signals. Most of what you need is on the free tier.
App builder / platform
Architecture patterns, account models, fee monetization, and the full execution stack across every venue.
Active trader / fund
The combined data + execution loop. Discover, signal, size, execute, monitor.
AI agent developer
Drop the MCP server into Claude, Cursor, or Codex. Five recipes for common agent tasks.
What’s on each surface
| Surface | Base URL | Key | When to reach for it |
|---|---|---|---|
| Data API | api.predexon.com | Data API key | Markets, prices, candles, trades, wallets, smart money. Free on most endpoints. |
| Trading API | trade.predexon.com | Trading API key | Place orders across venues, manage accounts, fund/withdraw. Free on every endpoint. |
| WebSocket | wss.predexon.com | Data API key | Live trades, orderbook, pending-trade signals. Dev plan and up. |
| MCP server | npx predexon-mcp | Data API key | AI agents — same data through one drop-in package. |
trade.predexon.com. Keys are not interchangeable — using one against the wrong surface returns 401 / 403.
Troubleshooting
401 / 403 errors
401 / 403 errors
- Verify your key is in the
x-api-keyheader (lowercase, hyphenated). - Check you’re sending the right key for the surface: Data API key for
api.predexon.comandwss.predexon.com, Trading API key fortrade.predexon.com. Mixing them returns401 / 403. - Free plan can’t hit Smart Money, Cross-Venue Matching, Binance, or WebSocket — those need Dev or higher.
- WebSocket connection rejected? Same gating — see Rate Limits.
429 Too Many Requests
429 Too Many Requests
You’ve hit your rate limit. Free is 1 req/s, Dev is 20 req/s, Pro is 100 req/s. Implement exponential backoff. See Best Practices for the pattern we recommend.
Empty results
Empty results
Most list endpoints accept
status, sort, limit parameters — try removing filters one at a time. Markets that were resolved more than a few weeks ago may be archived and need ?archived=true.Where do I see all endpoints?
Where do I see all endpoints?
Every endpoint is documented under Data & Signals (data) and Unified Execution Infra (trading). Each page has an interactive playground.
Need help?
Discord
The fastest way to get unblocked. Engineering reads every message.
team@predexon.com for anything that doesn’t fit Discord.