kalshi-mcp-server

A Model Context Protocol server for Kalshi prediction markets. Native RSA-PSS auth, async token-bucket rate limiting, two-step prepare/confirm order flow with safety caps, optional bundled OAuth proxy for remote-MCP deployments, 26 tools + 4 resources across REST and WebSocket. MIT, designed to be forked.

Works with any MCP client — locally via stdio (Claude Desktop, Claude Code, Cursor, Zed, Continue, Cline, Goose, etc.) or remotely as a self-hosted HTTP server (claude.ai custom connectors today, any OAuth-capable MCP client in the future).

⚠️ This software lets an LLM place trades. Read DISCLAIMER.md before deploying. Trading prediction markets involves substantial risk of loss. AI agents make mistakes — sometimes confidently. The authors are not liable for any losses. Test in demo (KALSHI_ENV=demo, KALSHI_TRADING_ENABLED=0) until you understand the failure modes.

Status — alpha. Auth (REST + WS), rate limiting, safety controls, 26 tools across REST + live channels, and 4 resources are in place. A long-lived multiplexed WebSocket session and kalshi://markets/{ticker}/orderbook live resource are planned for v0.2.

Why this server

Most existing Kalshi MCPs are thin wrappers around a handful of REST endpoints. This one aims to be:

• Native Kalshi. Real RSA-PSS signer that handles the gotchas (path-without-query-string, ms timestamps, separate demo/prod keys).
• Rate-limit aware. Client-side token bucket mirrors Kalshi's 2026 read/write budget model, so the server can't spam the API into a 429.
• Safe by default. Refuses to start against prod without an explicit opt-in flag. Refuses to write without a separate trading-enabled flag. Order-time controls (size cap, daily cap, cash reserve) are all operator-configurable.
• Hosted-deploy friendly. Accepts the private key as either a file path OR an env var with inline PEM, so it works on platforms without filesystem mounts.
• Fork-able. MIT, no personal data, CI/CD set up so PR contributions flow through main without ever triggering a production deploy — only tagged releases (v*) do. Your fork's deployment stays decoupled from this repo's, and your fork's contributors can't affect what you run.

Install

From source (the only option until v0.1 is published)

git clone https://github.com/cejor6/kalshi-mcp-server.git
cd kalshi-mcp-server
uv sync

Docker

docker pull ghcr.io/cejor6/kalshi-mcp-server:latest

(Image only exists once a v* tag is published. See DEPLOY.md.)

Configure

1. Generate a Kalshi API key at https://kalshi.com/account/profile (or the demo equivalent at https://demo.kalshi.co/account/profile). Save the private key — it is shown ONCE.

2. Put your secrets in one .env file. A good location for the MCP-client use case is ~/.kalshi/.env (outside any repo). For local dev, the repo's own .env (gitignored) works too.

cp .env.example ~/.kalshi/.env
# edit ~/.kalshi/.env

3. At minimum, set:

KALSHI_API_KEY_ID=<your-key-id>
KALSHI_PRIVATE_KEY_PATH=/absolute/path/to/your_kalshi_private_key.pem
KALSHI_ENV=demo

For prod, also set:

KALSHI_ENV=prod
KALSHI_ALLOW_PROD=1
KALSHI_TRADING_ENABLED=1   # only if you want writes

How env vars are resolved

On startup, the server resolves config in this order (highest wins):

1. Values already in the process environment — set in the MCP client config's env: block, or exported in your shell.
2. .env file — loaded from --env-file PATH if you pass that flag, otherwise from ./.env in the current working directory if it exists. Variables already in the environment from step 1 are not overridden.

So you can put secrets either inline in the MCP config (env:) or in a file the config points at (--env-file). You don't need to do both.

Use with an MCP client (stdio)

Every MCP stdio client uses the same shape: a command to launch the server, optional args, optional env. The differences are just the file/UI where you put the config.

Three install patterns work — pick whichever fits your environment.

Pattern A — pipx install (cleanest, recommended once published)

Installs kalshi-mcp to a globally-available, isolated environment. pipx is the modern Python tool for this:

pipx install kalshi-mcp-server

MCP client config then collapses to:

{
  "mcpServers": {
    "kalshi": {
      "command": "kalshi-mcp",
      "args": ["--env-file", "/Users/you/.kalshi/.env"]
    }
  }
}

Update with pipx upgrade kalshi-mcp-server when you want the latest.

Pattern B — uv run against a local clone

Best if you've cloned the repo and have uv installed. Point the MCP client at uv with --directory:

{
  "mcpServers": {
    "kalshi": {
      "command": "uv",
      "args": [
        "run",
        "--directory", "/absolute/path/to/kalshi-mcp-server",
        "kalshi-mcp",
        "--env-file", "/Users/you/.kalshi/.env"
      ]
    }
  }
}

uv run activates the project's venv automatically. Update with git pull + restart the MCP client. Useful for development / hacking on the server itself.

Pattern C — Docker against the public image

Best for users without Python installed, or who prefer container isolation:

{
  "mcpServers": {
    "kalshi": {
      "command": "docker",
      "args": [
        "run", "--rm", "-i",
        "-v", "/Users/you/.kalshi/demo.pem:/secrets/demo.pem:ro",
        "-e", "KALSHI_API_KEY_ID=<your-key-id>",
        "-e", "KALSHI_PRIVATE_KEY_PATH=/secrets/demo.pem",
        "-e", "KALSHI_ENV=demo",
        "ghcr.io/cejor6/kalshi-mcp-server:latest"
      ]
    }
  }
}

The -v mount bind-mounts your PEM file read-only into the container; KALSHI_PRIVATE_KEY_PATH points at that path. Secrets live in the JSON config — fine for a single-user machine.

Where to put this config:

If you'd rather inline secrets in the MCP config (acceptable for local dev where the config file is on your own machine):

{
  "mcpServers": {
    "kalshi": {
      "command": "kalshi-mcp",
      "env": {
        "KALSHI_API_KEY_ID": "your-key-id",
        "KALSHI_PRIVATE_KEY_PATH": "/path/to/your/private_key.pem",
        "KALSHI_ENV": "demo"
      }
    }
  }
}

Why not just .env in the project dir? MCP clients spawn the server as a subprocess from their own working directory (typically your home dir on macOS/Linux, the client's install dir on Windows), so a .env sitting in this repo wouldn't get found. Hence --env-file to point at it explicitly. Running the server directly from the project dir (no client) still works without flags — the CLI auto-loads ./.env when launched there.

Use as a remote MCP service

For clients that don't speak local stdio — currently the main one being claude.ai's custom connector form, which only supports OAuth-protected HTTP — host the server somewhere reachable and point the client at it. The OAuth proxy is bundled with the server; you just need to configure it.

See DEPLOY.md for an end-to-end walkthrough using Render + GitHub OAuth + Upstash Redis. Other image-deploy hosts (Fly.io, Cloud Run, ECS, Railway) work the same way — Render is just the worked example.

Tools

Write tools require KALSHI_TRADING_ENABLED=1. kalshi_prepare_order runs local safety checks and returns a confirmation_id; nothing is sent to Kalshi until you call kalshi_confirm_order with that token. Cancel and decrease bypass the trading-enabled flag — they only reduce exposure.

Listing markets for an LLM: kalshi_get_markets / kalshi_get_market accept minimal=true to project each market down to a small whitelist of triage fields (ticker, prices, sizes, volume, status, close time). Prefer this over compact=true for scanning — compact is a blacklist and barely shrinks multivariate (KXMVE…) combo markets, whose bulk lives in custom_strike / mve_selected_legs / long sub-titles. Pass a custom fields="ticker,yes_bid_dollars,…" to override the default whitelist. View precedence is fields > minimal > compact > full. kalshi_get_event / kalshi_get_events accept the same minimal / fields for their nested markets (the event objects themselves only have the compact view).

Don't gate on liquidity_dollars: Kalshi currently returns it as 0.0000 on every market, even deep books — measure liquidity from the orderbook (best bid/ask + resting size) plus volume_24h_fp / open_interest_fp. It is stripped from compact and minimal views.

Finding tradeable markets: the default open listing is dominated by multivariate (KXMVE…) combo markets with empty/one-sided books. Pass mve_filter="exclude" to kalshi_get_markets to drop them server-side, or use kalshi_find_liquid_markets — it excludes combos, ranks by 24h volume, and returns a short minimal-projection shortlist. (Kalshi has no server-side sort, so the helper's ranking is over a bounded scan window, reported as scanned in the result.)

Event ticker vs market ticker: a market ticker carries an outcome suffix (…PITHOU-HOU); an event ticker (…PITHOU) does not. Passing an event ticker to kalshi_get_market / kalshi_get_orderbook / kalshi_get_markets used to fail silently (404, or an empty book/list read as "no liquidity"). These tools now detect that case and raise an actionable hint naming the real market tickers instead.

Resources

A WebSocket-backed live-orderbook resource (kalshi://markets/{ticker}/orderbook) is planned — for now, use the kalshi_get_live_orderbook tool which opens a transient WS, samples the book, and returns the current snapshot + delta arrival rate.

Safety model

This server is deliberately conservative for the same reason your bank's ATM is — small mistakes shouldn't cost large amounts.

• KALSHI_ENV=prod requires KALSHI_ALLOW_PROD=1. The server refuses to start without both.
• All write tools require KALSHI_TRADING_ENABLED=1. The default is read-only.
• Per-order caps (MCP_MAX_ORDER_SIZE_USD, MCP_DAILY_LIMIT_USD, MCP_MAX_CONTRACTS_PER_ORDER, MCP_CASH_RESERVE_USD) are checked before the request reaches Kalshi.
• Tighten limits at runtime, no redeploy. Those env vars are the hard ceiling. The kalshi_set_safety_limits tool can tighten any limit on a running server (e.g. a fast clamp-down) but can never loosen one past its env ceiling — the three caps only go down, the cash reserve only goes up. Raising a ceiling still requires changing the env var and redeploying. The limits in force vs. their ceilings show up in kalshi_get_environment and kalshi://environment. Set MCP_REDIS_URL to make runtime changes survive a restart (otherwise they reset to the env ceilings on reboot).

See AGENTS.md for the full design.

Deployment

Use it locally as a stdio server with any MCP client, or run it as a remote HTTP MCP behind an OAuth proxy.

For remote deployment, the recommended setup is image-deploy: a production host (Render, Fly.io, Cloud Run, ECS, anything that supports pulling container images) pulls the image that's built and pushed when you tag a release (git tag v0.1.0). This decouples deployments from PR merges — PRs to main only ever run tests, never push a new image — so a malicious or careless PR cannot affect what's running in your container.

See DEPLOY.md for the rationale and a worked example with Render.

Contributing

PRs welcome. Read CONTRIBUTING.md first — there are a few rules around auth changes, secret hygiene, and test conventions.

License

MIT. See also DISCLAIMER.md — the MIT license disclaims warranty; DISCLAIMER.md spells out the trading- and AI-specific risks you're accepting by using this software.

Acknowledgments

• FastMCP — MCP framework.
• Kalshi — the underlying API.