Polymarket Market Maker

A market-making strategy that places GTC (Good-Till-Cancelled) limit orders on both sides of liquid Polymarket prediction markets, capturing the bid/ask spread.

Strategy

1. Market Selection: Finds active markets with:

   • 24h volume > $10,000 (liquid enough to fill)
   • Price (YES probability) between 0.15 and 0.85 (avoids near-certain outcomes)
   • Resolves > 4 hours away (enough time to get fills)
   • No taker fees (is_paid=False) — 10% fee kills the edge

2. Pricing: Fetches the live CLOB midpoint for each market and quotes:

   • YES buy limit at mid - 0.02 (2¢ below mid)
   • NO buy limit at (1 - mid) - 0.02 (2¢ below NO mid)

3. Order Management: Cancels existing open orders before placing new ones each run.

4. Limits: Max $5 per order, max 3 markets per run.

Requirements

Environment variables (required):

Python dependency: simmer-sdk — install with pip install simmer-sdk

Setup

export SIMMER_API_KEY=sk_live_...         # required
export TRADING_VENUE=sim                   # optional: paper mode with $SIM
pip install simmer-sdk

Usage

# Dry run (default)
python market_maker.py

# Live trading
python market_maker.py --live

# Show current positions
python market_maker.py --positions

# Show config
python market_maker.py --config

# Set config
python market_maker.py --set max_order_usd=10.0

Config (env vars)