Polymarket API for Developers: Data, CLOB, and Polygon RPС

Source: Dev.to

Gamma API – Market Discovery

• Public, no authentication required.
• Exposes Events (top‑level questions) and Markets (specific tradable outcomes).
• Each market includes an outcomePrices array that maps 1:1 to outcomes, representing implied probabilities (e.g., 0.62 = 62 % chance of YES).
• Filterable by active status, 24 h volume, tags, open/closed state, etc.
• Important: Verify enableOrderBook: true before assuming a market has live CLOB liquidity.

CLOB – Hybrid Trading Engine

The CLOB handles off‑chain order matching and on‑chain EIP‑712 settlement.

• Access: Official SDKs (TypeScript, Python, Rust) or raw REST.
• Authentication:
  1. L1 – Wallet signatures generate API credentials without spending gas.
  2. L2 – Credentials are used for fast HMAC‑signed requests on every order call.
• Order Types:
  • GTC – Good‑Till‑Cancelled (rests on book)
  • GTD – Good‑Till‑Date (time‑bound)
  • FOK – Fill‑Or‑Kill (all‑or‑nothing)
  • FAK – Fill‑And‑Kill (fill what’s available, cancel the rest)
• Pre‑order checks: valid EIP‑712 signature, sufficient USDC.e balance, approved CTF Exchange allowances, and valid L2 credentials.

Data API – User‑Level Analytics

Provides detailed analytics for a wallet:

• Current positions across markets.
• Full trade history with timestamps, sizes, and realized/unrealized P&L.
• Activity feeds per wallet.

Useful for building dashboards or analyzing strategy performance over time.

WebSocket – Real‑Time Updates

Four subscription channels:

Production note: Polymarket cancels all open orders when an authenticated session becomes inactive. Bots must send periodic heartbeats to keep the session alive.

Step‑by‑Step Integration Overview

1. Set up a Polygon wallet and fund it with POL.
2. Deposit USDC.e to your Polymarket profile address.
3. Derive L2 API credentials from your wallet.
4. Run client.setAllowances() once to approve the CTF Exchange.
5. Fetch a market via Gamma API.
6. Inspect the order book.
7. Place a limit order through the CLOB SDK or REST endpoint.
8. Subscribe to relevant WebSocket channels for real‑time fills.
9. Set up an OrderFilled event listener on the CTF Exchange for on‑chain confirmation.

These steps give you a foundation for analytics tools, automated trading bots, or custom interfaces.

Official & Community Tooling

• clob-client (TypeScript) – Order placement & API credential handling.
• real-time-data-client – WebSocket subscriptions with built‑in reconnect logic.
• clob-order-utils – Low‑level EIP‑712 order signing.
• rs-clob-client (Rust).
• Polymarket Agents (Python) – Reference implementation for LLM‑based autonomous trading.
• Goldsky‑powered subgraphs – GraphQL endpoints for positions, order book, P&L, open interest.
• Polygon RPC – Production‑grade archive access and WebSocket via Chainstack.

Risks & Considerations

• Market risk: Incorrect predictions result in total loss of the committed amount.
• Liquidity risk: Thin markets may have insufficient depth.
• Oracle risk: Settlement delays can occur if outcomes are disputed.
• Regulatory risk: Geographic restrictions may apply; verify the legal status of prediction markets in your jurisdiction.
• Smart‑contract risk: As with any on‑chain platform, vulnerabilities may exist.

Only use funds you are prepared to lose and conduct appropriate due diligence.

Conclusion

The Polymarket API turns prediction markets into programmable infrastructure:

• Fast, low‑cost settlement on Polygon.
• USDC.e‑denominated trading.
• Clean primitives across Gamma (discovery), CLOB (execution), Data (analytics), and WebSocket (real‑time).
• Existing EVM tooling (Solidity, ethers.js, viem, Foundry) works without modification.

The ecosystem is still early, offering ample opportunity to build trading bots, probability dashboards, or analytics pipelines on top of well‑documented, audited contracts with transparent on‑chain history.

Read the full article on Chainstack Blog