Synth Overlay: Polymarket Edge Extension

[e35ventura]

Synth Overlay: Polymarket Edge Extension

Category: Best Prediction Markets Tool
Difficulty: Advanced
Synth Endpoints Used: get_polymarket_daily(), get_polymarket_hourly(), get_polymarket_range(), get_prediction_percentiles()

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What It Is

A Chrome extension for Polymarket that adds a live "fair value" layer directly on market pages. It tells users — in place — whether the current YES/NO price looks underpriced, overpriced, or fair based on Synth probabilities.

• Read-only decision overlay, not an auto-trader
• Appears only on markets Synth supports
• Converts Synth forecasts into an instant edge signal at the exact point of decision on Polymarket

Core UX

1. Inline Badge (beside YES/NO prices)

Shows Fair, Market, and Edge at a glance.

State	Display
Underpriced	YES Edge +6.2% (green)
Overpriced	YES Edge -4.1% (red)
Fair	Fair ±0.5% (neutral)

2. Mini Detail Card (on click)

• Now signal (1h horizon)
• By close signal (24h horizon)
• Confidence level
• "No trade" warning if uncertainty is high or signals conflict

3. Optional Slide-Out Panel

• Full explanation in plain English
• Why the signal exists
• What would invalidate it
• Last update timestamp

Signal Language

Signal	Meaning
Strong Edge	Meaningful mispricing + aligned 1h/24h signals
Moderate Edge	Edge exists but weaker confidence or mixed horizons
No Edge	Fairly priced, conflicting signals, or low-quality setup

Auto-Matching Behavior

1. Extension reads Polymarket page title/metadata
2. Maps market to a Synth-supported asset + market type
3. If supported → overlay renders
4. If unsupported → overlay stays hidden (no clutter)

Design Principles

• Glanceable first — User should understand edge in under 2 seconds
• Contextual only — No clutter across the site. Overlay only where Synth mapping is valid
• Trust-forward — Always show confidence and uncertainty. Never present fake precision
• Trader-native — Sits next to price controls, where the user already acts

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Submission Requirements

• Demo video — Screen recording showing the extension running on a live Polymarket page
• 1-page technical explanation — Include as tools/synth-overlay/README.md. Should cover what the tool does, how it works, and how it uses Synth data
• Tests in tools/synth-overlay/tests/

Getting Started

This repo includes everything you need to build without a Synth API key:

from synth_client import SynthClient

client = SynthClient()  # auto-loads mock data when no API key is set

# Get Synth vs Polymarket daily comparison
daily = client.get_polymarket_daily()
# Returns: synth_probability_up, polymarket price, current_outcome, etc.

# Get Synth vs Polymarket hourly comparison
hourly = client.get_polymarket_hourly()

# Get range-based market comparisons
ranges = client.get_polymarket_range()
# Returns: list of price range brackets with synth_probability vs polymarket_probability

# Get raw probability distribution for deeper analysis
forecast = client.get_prediction_percentiles("BTC", horizon="1h")

1. Fork the repo and clone it
2. Copy the template: cp -r tools/_template tools/synth-overlay
3. pip install -r requirements.txt
4. Build your tool using the SynthClient — it works immediately with mock data
5. Add tests in tools/synth-overlay/tests/
6. Open a PR when ready

See the README for the full endpoint reference and supported assets.