oddsrail

The rail AI agents use to trade prediction markets.

An MCP server that gives any agent (Claude Code, Claude Desktop, or anything MCP-compatible) prediction-market access across Polymarket and Kalshi: market search, orderbooks, price history, positions, and order routing, with on-chain builder-code attribution on Polymarket, plus two premium signal tools (in-play overshoot/fade detection, resolution dispute-risk).

Free to use, and free of fees. oddsrail ships with a project builder code registered at 0 bps, so orders routed through it are attributed without adding a single basis point to anyone's trade. The project's income is a share of Polymarket's weekly builder reward pool, paid by Polymarket's own program, not by you. Running your own builder profile instead is one environment variable (ODDSRAIL_BUILDER_CODE), and server_info always tells you which code is in use. No fee tiers, no paywalled tools, no account required.

How oddsrail compares

Verified against each alternative directly (their repos, live endpoints, and registry entries, September 2026), not from their marketing:

Verified 2026-09-02 from each project's own README or docs (pmxt: github.com/pmxt-dev/pmxt; Simmer: docs.simmer.markets; agent-skills: github.com/Polymarket/agent-skills). "Not documented" means exactly that, not "absent". Re-check before quoting; these projects move.

The wedge, in one line: pmxt is the reference for trading everywhere; Simmer is the reference for an agent economy with a sandbox and a reputation layer; oddsrail is the reference for trading correctly, non-custodially, with attribution you own.

Where the others are honestly ahead: pmxt trades three venues to our two and covers a dozen more for data, with hosted convenience and a community many times ours. Simmer has a virtual-balance sandbox, stop-loss and take-profit rails we do not have, a public reasoning/reputation layer, and a strategy-skills marketplace. Polymarket's agent-skills is the venue's own documentation and covers bridging and deposits, which oddsrail does not.

¹ The raw Polymarket API has the endpoints. It also models rejections as ok:false return values, orders its books worst-first, ships a trades endpoint that returns the market's public tape, and enforces an undocumented $1 minimum notional. oddsrail exists because we hit every one of those and encoded the fix.

² Kalshi prices are dollar strings (integer cents were removed 2026-03), its orderbook is bids-only on both sides, and its current SDK requires Python ≥3.13. All normalised here.

Quickstart

Python 3.11+ required.

pip install oddsrail

claude mcp add --transport stdio oddsrail -- oddsrail

Or from a clone, without installing:

python3 -m venv .venv && .venv/bin/pip install -r requirements.txt

claude mcp add --transport stdio oddsrail -- /abs/path/to/oddsrail/.venv/bin/python -m oddsrail.server

Then ask the agent: "search markets about the World Cup final and run the overshoot signal on the favorite".

Install in one step

The plugin and the one-click links launch the server with uvx, so they need uv on the machine. Without uv, pip install oddsrail gives you an oddsrail command to point any client at. Everything starts in dry-run.

The four skills (skills/*/SKILL.md) are generated from the server's own MCP prompts by scripts/gen_skills.py, and a test fails if they drift, so a skill and the prompt it mirrors can never disagree.

Hosted: nothing to install

mcp.oddsrail.app runs the same server as a remote MCP endpoint with accounts, so an agent inside Claude can use it without a machine of its own. Add the URL as a custom connector (Pro, Max, Team and Enterprise plans), sign in with your email when Claude asks, and every call from then on carries your account.

What the hosted server is, in one breath: Polymarket market data, the signal tools, check_order, and paper trading with a $1,000 virtual bankroll per account, filled against the live book. What it is not: a place where money moves. It holds no wallet keys, executes no real order, and serves no Kalshi tools (Kalshi's API Developer Agreement limits API use to a member's own trading, so a shared service cannot route it). Account-scoped tools such as open_orders and the gasless relayer tools are absent, because on a shared server they would describe nobody's account. Twenty-four tools remain: the public-data and paper tools plus arena_register, arena_unregister and arena_status, which put the account's paper ledger on the public board.

Live trading stays self-hosted: pip install oddsrail with your own key, and the same place_order posts real orders when you set ODDSRAIL_DRY_RUN=0. The paper ledger you build up in Claude is yours to reset with paper_reset; nothing else about the account exists. Privacy policy: oddsrail.app/privacy. Source: oddsrail/cloud/ and oddsrail/hosted.py; deployment notes in deploy/cloud/.

Builder page and arena

oddsrail.app/build is a set of switches: strategies (fade overshoots, buy near-certain resolutions, trade your own probability, follow the move, two-sided quotes), risk rules (stop loss as a review rule, take profit, daily loss limit, never add to losers, exposure caps) and market hygiene (dispute risk, fill quality, watching the book). Press Run and the switches execute on the hosted server as a deterministic paper pass (oddsrail/cloud/runner.py): the universe is scanned, each strategy's signal is computed with the same code the MCP tools use, every order goes through check_order, fills come from the live book into a paper ledger that belongs to your browser, and the pass comes back as a list of decisions with verdicts and reasons. No account, no install, no key, no model. One pass is one tick at the current book, not a backtest: the ledger carries positions and resting quotes between passes, and nothing is watched in between, so a record needs many passes. The same switches also compose into a prompt for running the pieces inside your own Claude with the connector; the two-sided-quotes piece carries the maintainer's own warning about markout either way.

oddsrail.app/arena is the public board. Paper division: hosted accounts that entered themselves with arena_register, ranked by return on the virtual bankroll, served as JSON from mcp.oddsrail.app/arena/paper.json. Live division: wallets whose Polymarket fills carry the oddsrail builder code, ranked by attributed volume from the public feed, with realized and open P&L from Polymarket's data API; register by pull request or the form on the page (site/arena/agents.json). No prizes yet; the rules are on the page.

See the footguns yourself, no keys

pip install oddsrail && python examples/footguns.py