Deep integration guide for Polymarket's CLOB API, Gamma API, and on-chain data. Use when building trading functionality, fetching market data, or implementing order execution.

Polymarket API Integration Skill Overview This skill provides comprehensive guidance for integrating with Polymarket's APIs and smart contracts. API Endpoints CLOB API (Central Limit Order Book) Base URL: https://clob.polymarket.com Authentication Levels Level 0 (Public) : Market data, orderbooks, prices Level 1 (Signer) : Create/derive API keys Level 2 (Authenticated) : Trading, orders, positions Key Endpoints Gamma API (Market Metadata) Base URL: https://gamma api.polymarket.com Python Implementation Patterns Initialize Client WebSocket Subscription Gamma API Client Order Types GTC (Good Till Cancelled): Stays until filled or cancelled GTD (Good Till Date): Expires at specified time FOK (Fill or Kill): Must fill entirely or cancel IOC (Immediate or Cancel): Fill what's available, cancel rest Fee Model Polymarket's taker only formula (docs.polymarket.com/trading/fees, fetched 2026 09 04): Where: C = contract count ($1 per contract at resolution) rate = taker fee rate (category dependent, makers never pay) p = fill price, a probability in [0, 1] (1 − p) = the fee term; maximized at p=0.5 (coin flip), vanishes at tails (p→0 or p→1) Category taker rates (charged in USDC): Category Rate Crypto 0.07 Sports / Economics / Culture / Weather / Other 0.05 Finance / Politics / Mentions / Tech 0.04 Geopolitics 0.00 Per market override : The CLOB market payload may carry maker base fee / taker base fee (historical field names), which is authoritative over the category table when present. These fields are in BASIS POINTS, not a dimensionless rate — taker base fee=700 means 0.07, not 700. Divide by 10 000 to get the rate FeeSchedule expects ( app/venues/polymarket/adapter.py does this at the two places it reads these fields) before building a FeeSchedule from the payload ( source="clob market" ) rather than from category rate() . Skipping the division is a 10,000× fee error. Maker fees : Always 0 on Polymarket CLOB; taker only venue. Price Calculations Error Handling Rate Limits Public endpoints: ~100 requests/minute Authenticated endpoints: ~1000 requests/minute WebSocket: Varies by subscription type Always implement exponential backoff and request queuing. Key Contract Addresses (Polygon)

polymarket-api