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):

VariableRequiredDescriptionSIMMER_API_KEY✅ YesYour Simmer API key — get it at simmer.markets/dashboard → SDK tabTRADING_VENUEOptionalpolymarket (default) or sim for paper trading with virtual $SIM

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

Setup#

bash

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

Usage#

bash

# 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)#

Env VarDefaultDescriptionSIMMER_MM_MAX_ORDER_USD5.0Max USD per limit orderSIMMER_MM_MAX_MARKETS3Max markets per runSIMMER_MM_MIN_VOL_24H10000Min 24h volume filterSIMMER_MM_SPREAD_OFFSET0.02How far below mid to quote (2¢)SIMMER_MM_MIN_PRICE0.15Min YES price to considerSIMMER_MM_MAX_PRICE0.85Max YES price to considerSIMMER_MM_MIN_HOURS_TO_RESOLVE4Min hours to resolution