Polymarket US — event contract trading via the retail API

This skill manages Polymarket US event-contract trades through the official retail REST API. Polymarket US is the CFTC-regulated Designated Contract Market operated by QCX LLC — fiat USD, fully off-chain, Ed25519 API-key auth. It is not polymarket.com (international); the API, auth, and custody all differ.

Public market data — events, markets, search, order books, best bid/offer — lives on the gateway host with no auth. Trading calls go to the API host with X-PM-Access-Key / X-PM-Timestamp / X-PM-Signature headers, the signature being Ed25519 over timestamp_ms + METHOD + path. Timestamps must be within 30 seconds of server time. Credentials come from environment variables at runtime, never hardcoded or logged.

The fee structure drives the strategy rules: the taker fee is Θ=0.0695 × C × p × (1−p) (up to $1.74 per 100 contracts at 50¢), while makers earn a rebate — so the skill insists on running the fee math before crossing any spread, since posting as a maker is materially cheaper on most prices. Prices are in cents 1–99, contracts pay $1.00 if correct and $0 if wrong.

Guardrails: there is no sandbox — every order is real money. Before placing any order, the agent presents market, side, size, price, and total cost and requires the user's explicit confirmation. Rate limit is 20 requests/second per key, a Thursday 6–8am ET maintenance window should be avoided, and settlement sources differ from Kalshi (Polymarket US weather markets settle on NWS reports), so same-topic cross-venue positions are never treated as arbitrage.