# Layer

> One API for prediction markets. Layer tells you which markets on Kalshi, Polymarket, Polymarket US, Hyperliquid and Novig are the same bet, with prices, fees and profit math. Orders go from the open-source Python SDK on your machine to each venue, with your own keys.

Base URL: https://uselayer.sh. Send a key as `authorization: Bearer lyr_…` (free, from https://uselayer.sh/dashboard), or call the paid endpoints with no key and pay per call with x402.

Every docs page is Markdown at its URL plus `.md`. All of them in one file: https://uselayer.sh/llms-full.txt

## Get started

- [Overview](https://uselayer.sh/docs/index.md): What Layer does today, in plain words.
- [Quickstart](https://uselayer.sh/docs/quickstart.md): Find the same bet on both venues, then price it on your machine.
- [Starter bot](https://uselayer.sh/docs/starters.md): Three small Python scripts that read live matched markets. Run one in your browser, then on your laptop with one paste.
- [Example bot: Spread](https://uselayer.sh/docs/spread.md): A bot you can clone and run, built on the SDK. Best venue and arbitrage across Kalshi and Polymarket US.
- [Example: Sports replay](https://uselayer.sh/docs/sports-replay.md): 38 recorded games on Kalshi and Polymarket US, replayed on one clock. Every arbitrage gap after fees, how long it lasted, and which venue moved first.

## Built on Layer

- [Signals](https://uselayer.sh/docs/signals.md): Follow the best Polymarket traders. See their track record, what they hold and every trade they make, and get a Telegram alert after they trade.
- [Breakdowns](https://uselayer.sh/docs/breakdowns.md): Paste a Polymarket wallet, ask in your own words, and an AI agent lays every trade out on a chart you can replay. BTC 15-minute markets, built on Layer's recorded order books.
- [Trader data](https://uselayer.sh/docs/trader-data.md): Every trade on Polymarket is public. See any trader's track record, win rate, what they hold and every trade they make, and follow them on Signals.

## Experiments

- [Nemi](https://uselayer.sh/docs/nemi.md): Our paper-trading experiment. Test a trading strategy with paper money on real Polymarket prices.

## Reference

- [API reference](https://uselayer.sh/docs/api.md): Endpoints, fields, errors.
- [Pay per call (x402)](https://uselayer.sh/docs/pay-per-call.md): No account, no API key. Agents pay per answer in USDC on Base with x402, from 1¢.
- [Markets](https://uselayer.sh/docs/markets.md): One market per real-world question, with every venue's listing of it.
- [Sports spreads and lag](https://uselayer.sh/docs/sports.md): Live spreads after fees and measured lead/lag for US sports game winners on Kalshi and Polymarket US.
- [Stream](https://uselayer.sh/docs/stream.md): Live sports and 15-minute crypto order books from Kalshi and Polymarket US over one WebSocket, with the spread after fees both ways.
- [Sandbox](https://uselayer.sh/docs/sandbox.md): Practice trading with simulated money at live prices, on Layer or on your own machine.
- [Python SDK](https://uselayer.sh/docs/sdk.md): Trade prediction markets from Python with your own venue keys.
- [Backtest data](https://uselayer.sh/docs/backtest-data.md): The Python SDK's event format, and how to import history you already have.
- [Command line](https://uselayer.sh/docs/uselayer.md): The `uselayer` command: matches, lookups and profit checks from your terminal.
- [MCP server](https://uselayer.sh/docs/mcp.md): Give Claude Code, Cursor or any MCP client Layer's matched markets as tools, with your API key.

## How it works

- [How matching works](https://uselayer.sh/docs/matching.md): How Layer decides two markets are the same bet.
- [How we measure sports gaps](https://uselayer.sh/docs/sports-method.md): How Layer records Kalshi and Polymarket US sports order books and measures arbitrage gaps and lead/lag after fees, what we found, and the limits of the data.

## Help

- [Feature requests](https://uselayer.sh/docs/feature-requests.md): Ask for something Layer doesn't do yet, or tell us what's in your way.

## Machine-readable

- [MCP server](https://uselayer.sh/mcp): Streamable HTTP, with your key as the header `authorization: Bearer lyr_…`. Tools: find_matches, lookup_match, check_profit (read-only)
- [OpenAPI, the whole API](https://uselayer.sh/v0/openapi.json): every endpoint and its inputs
- [OpenAPI, pay per call](https://uselayer.sh/openapi.json): the endpoints an agent can pay for with no key, their inputs, an example answer and the price of each
- [Starter bots](https://uselayer.sh/docs/starters.md): three short Python files, each at https://uselayer.sh/starters/<file>.py
- [Python SDK](https://pypi.org/project/uselayer/): `pip install uselayer`; the package ships its own AGENTS.md and llms.txt