langbot-mcp

MCP server for Langbot, the data and simulation layer for every market on Kalshi and Polymarket: search any market and read its price history, compare the same question across both venues, replay past events against the order books Langbot recorded, and, for markets that settle on what is said (mention markets are one example), the live record of the event with verifiable receipts. Data, never trading signals or advice: the optional strategy tools are off unless you opt in.

Over local stdio, search_markets and get_market_history work without a token.

uvx langbot-mcp                      # stdio — what Claude Code / Cursor / Claude Desktop / Codex run
langbot-mcp --http                   # streamable HTTP on 0.0.0.0:8001 at /mcp (hosted: https://mcp.langbot.ai/mcp); multi-tenant, token per request
langbot mcp install claude-code      # one-command install (also: cursor, claude-desktop, codex, all)

Manual client entry:

{ "mcpServers": { "langbot": { "command": "uvx", "args": ["langbot-mcp"], "env": { "LANGBOT_API_TOKEN": "lb_…" } } } }

Hosted, for clients that send headers (Cursor, Claude Code --transport http):

{ "mcpServers": { "langbot": { "url": "https://mcp.langbot.ai/mcp", "headers": { "Authorization": "Bearer lb_…" } } } }

Auth. Each tool's _meta has langbot/auth (none | token: what the feed needs, which is what applies over local stdio) and langbot/auth_hosted (always bearer). The hosted endpoint needs Authorization: Bearer lb_… on every tool call and resource read, including none tools; without a token, run it locally (uvx langbot-mcp).

Tools

Langbot Sim

Opt-in strategy tools (LANGBOT_MCP_STRATEGY_TOOLS=1)

Off by default: Langbot serves data, not signals. Set LANGBOT_MCP_STRATEGY_TOOLS=1 in the client's env to list and allow these three; without it they are hidden and cannot be called.

Terminal: what's live, what's priced, what's been said, how often before

Each docstring says when an agent should reach for it. Rights (CONTRACTS §10): get_transcript returns full text for public_domain / licensed sources and phrase facts only for restricted / unknown ones; get_calendar and get_market_context carry rights so an agent knows in advance.

Resources: langbot://events/live, langbot://events/{id}/transcript, langbot://latency, langbot://calendar, langbot://context/{ticker}, langbot://markets/{ticker}/brief, and the two live (subscribable) ones below.

Live push

How an agent subscribes depends on the MCP revision its client negotiated; the server serves both:

• 2025-11-25 and older: resources/subscribe {uri}; on each notifications/resources/updated for the URI, resources/read it. resources/unsubscribe (or disconnecting) stops it.
• 2026-07-28: subscriptions/listen with resource_subscriptions: [uri, …]; the same notification rides the listen stream (the SDK's ListenHandler), closing it unsubscribes.
• neither: watch_event in a loop with the returned cursor.

Upstream is one WS /v1/stream per token (stdio: one; hosted HTTP: one per tenant), filtered to the subscribed events and types=phrase_detected, re-filtered with {"op":"subscribe"}, closed when nothing is subscribed, reconnected with jittered backoff (1 → 30 s) and backfilled from the transcript after a reconnect. See live.py. Push over HTTP needs the default stateful streamable HTTP (SSE responses, the GET stream); with stateless_http / json_response only watch_event works.

Paying per call

Some feed endpoints are sold by the call (CONTRACTS §17): replay bundles ($0.50), history ($0.05), evidence packs ($0.25), provenance reports ($0.10), facts ($0.02) — initial list prices. Tools that map to them carry _meta langbot/per_call_usd next to the plan fields, so an agent can read the price before calling, and get_pricing passes through the feed's per_call (always) and x402 ({enabled: false} or {enabled: true, x402_version, scheme, network, pay_to, asset, asset_decimals, facilitator, max_timeout_seconds, headers, …}) sections.

The MCP server holds no wallet. When the feed answers an x402 v2-shaped 402, the tool returns a structured error instead of a bare failure:

{"ok": false, "error": "payment_required", "status": 402, "price_usd": 0.5, "x402Version": 2,
 "accepts": [{"scheme": "exact", "network": "eip155:8453", "amount": "500000", "asset": "0x…USDC", "payTo": "0x…", "maxTimeoutSeconds": 60, "extra": {"name": "USD Coin", "version": "2"}}],
 "pricing_url": "https://langbot.ai/.well-known/langbot-pricing.json", "hint": "…"}

The agent can then pay with its own wallet through the SDK (LangbotClient(x402_wallet=…) in langbot-sdk[x402], or @langbotai/sdk with x402Wallet), or ask the user for a plan token. A 402 that is not x402-shaped (a plan gate) is reported as before.

Env

Tokens in HTTP mode

--http is multi-tenant: every request must carry Authorization: Bearer lb_… and that token is used for the feed call; the server's LANGBOT_API_TOKEN is ignored. Tool calls and resource reads without a token are refused with a message pointing at https://langbot.ai/app/tokens (listing tools still works). The header is read with fastmcp.server.dependencies.get_http_headers(include={"authorization"}); see get_client() and TokenGate in server.py.

Compliance shape

The server emits facts (what was said, when) and runs nothing live. The strategy tools are opt-in (LANGBOT_MCP_STRATEGY_TOOLS=1); when enabled, run_paper only starts demo-mode strategies on the user's local daemon, and draft_strategy output is reviewed by the user before langbot run. Live trading requires --mode live plus LANGBOT_I_UNDERSTAND_LIVE=1 on the user's machine.

Develop

uv run --package langbot-mcp pytest services/mcp -q
docker build -f services/mcp/Dockerfile -t langbot-mcp .   # from repo root

Registry metadata: server.json (MCP registry, mcp-publisher publish) and smithery.yaml.

License

MIT (LICENSE in this directory). langbot-mcp is published on PyPI; it is a thin client over the hosted Langbot feed, which is a proprietary service.