Polymarket

Polymarket — Prediction Market Data

Query prediction market data from Polymarket using their public REST APIs. All endpoints are read-only and require zero authentication.

See references/api-endpoints.md for the full endpoint reference with curl examples.

When to Use

• User asks about prediction markets, betting odds, or event probabilities
• User wants to know "what are the odds of X happening?"
• User asks about Polymarket specifically
• User wants market prices, orderbook data, or price history
• User asks to monitor or track prediction market movements

Key Concepts

• Events contain one or more Markets (1:many relationship)
• Markets are binary outcomes with Yes/No prices between 0.00 and 1.00
• Prices ARE probabilities: price 0.65 means the market thinks 65% likely
• outcomePrices field: JSON-encoded array like ["0.80", "0.20"]
• clobTokenIds field: JSON-encoded array of two token IDs [Yes, No] for price/book queries
• conditionId field: hex string used for price history queries
• Volume is in USDC (US dollars)

Three Public APIs

1. Gamma API at gamma-api.polymarket.com — Discovery, search, browsing
2. CLOB API at clob.polymarket.com — Real-time prices, orderbooks, history
3. Data API at data-api.polymarket.com — Trades, open interest

Typical Workflow

When a user asks about prediction market odds:

1. Search using the Gamma API public-search endpoint with their query
2. Parse the response — extract events and their nested markets
3. Present market question, current prices as percentages, and volume
4. Deep dive if asked — use clobTokenIds for orderbook, conditionId for history

Presenting Results

Format prices as percentages for readability:

• outcomePrices ["0.652", "0.348"] becomes "Yes: 65.2%, No: 34.8%"
• Always show the market question and probability
• Include volume when available

Example: "Will X happen?" — 65.2% Yes ($1.2M volume)

Parsing Double-Encoded Fields

The Gamma API returns outcomePrices, outcomes, and clobTokenIds as JSON strings inside JSON responses (double-encoded). When processing with Python, parse them with json.loads(market['outcomePrices']) to get the actual array.

Rate Limits

Generous — unlikely to hit for normal usage:

• Gamma: 4,000 requests per 10 seconds (general)
• CLOB: 9,000 requests per 10 seconds (general)
• Data: 1,000 requests per 10 seconds (general)

Limitations

• This skill is read-only — it does not support placing trades
• Trading requires wallet-based crypto authentication (EIP-712 signatures)
• Some new markets may have empty price history
• Geographic restrictions apply to trading but read-only data is globally accessible

Source: NousResearch/hermes-agent → skills/research/polymarket/SKILL.md