Polymarket Us MCP Server

polymarket-us

Market data from Polymarket US (polymarket.us) — the CFTC-regulated, US-licensed prediction-market exchange. This is a SEPARATE venue from the offshore Polymarket platform (see the polymarket pack) and from Kalshi (see the kalshi pack): different company, different markets, different slugs. A slug from one venue never resolves on another, and every response here carries venue: "polymarket-us" plus data_as_of so a caller comparing across packs never silently mixes venues.

Part of Pipeworx — an MCP gateway connecting AI agents to 1866+ live data sources. This is an independent, unofficial integration — not affiliated with, endorsed by, or published by the upstream provider.

Upstream: https://gateway.polymarket.us (docs: https://docs.polymarket.us/api-reference/introduction). This is Polymarket US's public market-data host — no auth, no account, no API key for any endpoint this pack calls. A separate authenticated host, api.polymarket.us, handles order placement and portfolio/account data; this pack is read-only market data only, same posture as polymarket and kalshi.

Tools

All five need a market slug, which polymarket_us_search returns.

Auth

Keyless. The gateway.polymarket.us market-data endpoints need no API key, account or authentication of any kind — verified live, including from a Cloudflare Workers edge location (wrangler dev --remote), since the sibling kalshi pack discovered its upstream filters Cloudflare egress on some endpoints and this one does not share that problem.

Data sources

• GET /v1/search — full-text search across events/markets.
• GET /v1/markets — filterable market listing (used for category/volume browsing when polymarket_us_search is called without a query).
• GET /v1/markets/{slug}/bbo — best bid/offer (lightweight top-of-book).
• GET /v1/markets/{slug}/book — full order book + session stats.
• GET /v1/price-history?symbol={slug}&fidelity=…&fixedInterval=… — historical Yes/No display prices.
• GET /v1/markets/{slug}/settlement — settlement price; 404s until the market resolves. A bare 404 is ambiguous (open market vs. nonexistent slug), so this pack disambiguates with a cheap GET /v1/markets?slug= existence check before reporting settled: false for a market that exists, or error: "not_found" for a slug that doesn't — never "still open" for a market that was never real.

Notes

• Price history's longPrice/shortPrice (mapped here to yes_price / no_price) are display prices — yes_price is normally derived from the best ask and no_price from one minus the best bid — so they preserve the bid/ask spread and CAN sum to more than 1.0. That is expected, not a data error.
• The settlement endpoint returns a price only, no timestamp. Resolution- audit integration (fleet #1909) is explicitly out of scope for this pack — it would need (a) a stable per-market settlement timestamp, which this API does not expose, and (b) a bulk "settled since <date>" filter, which /v1/markets also does not have (only a boolean closed flag) — without one, auditing settlements means polling every known slug.
• /v1/search has no category filter (only seriesIds, marketType, time-range and status). polymarket_us_search's category argument is therefore browse-mode only (routes to /v1/markets) and is silently ignored when query is set — the tool description says so.

Quick Start

Add to your MCP client (Claude Desktop, Cursor, Windsurf, etc.):

{
  "mcpServers": {
    "polymarket-us": {
      "url": "https://gateway.pipeworx.io/polymarket-us/mcp"
    }
  }
}

What this endpoint actually serves

tools/list at https://gateway.pipeworx.io/polymarket-us/mcp returns the tools in the table above plus the shared Pipeworx meta-tools — ask_pipeworx, discover_tools, search_within, remember/recall and the rest of the gateway-wide set. So the tool count you see is larger than this table: a single-pack endpoint currently lists roughly 30 shared tools alongside the pack's own. The connection's initialize response states its exact scope, and is the authoritative answer for a given day.

This is deliberate, not multiplexing by accident. The meta-tools are what let a scoped connection answer a question this pack does not cover — via ask_pipeworx, which routes across the whole catalog — without you adding a second MCP server. There is currently no way to mount a pack endpoint without them; if the extra schemas cost you more context than the routing is worth, connect to the full gateway once rather than to several pack endpoints.

Or connect to the full Pipeworx gateway to get every pack's tools listed directly, instead of just this one's:

{
  "mcpServers": {
    "pipeworx": {
      "url": "https://gateway.pipeworx.io/mcp"
    }
  }
}

Both URLs reach the same gateway and the same 1866+ data sources. The only difference is which pack's tools are listed directly; ask_pipeworx reaches all of them from either one.

No MCP client? Call it over HTTP

curl -X POST https://gateway.pipeworx.io/v1/tools/polymarket_us_search \
  -H 'Content-Type: application/json' \
  -d '{"query":"fed funds","limit":3}'

No account needed for the first calls. Inspect any tool: GET https://gateway.pipeworx.io/v1/tools/polymarket_us_search. Find one: POST https://gateway.pipeworx.io/v1/tools/search_packs with {"query":"..."}.

Run it from npm

@pipeworx/mcp-polymarket-us is a local stdio bridge to the Pipeworx gateway: your MCP client starts it with npx, and it forwards every call to the same https://gateway.pipeworx.io/polymarket-us/mcp endpoint shown above. It needs network access; there is no offline mode.

{
  "mcpServers": {
    "polymarket-us": {
      "command": "npx",
      "args": ["-y", "@pipeworx/mcp-polymarket-us"]
    }
  }
}

Without a key it calls anonymously, capped at 50 calls a day. A free account raises that to 200 a day: get a key at https://pipeworx.io/signup and add "env": { "PIPEWORX_API_KEY": "<your key>" } to the server entry. The key is sent as a Bearer token, the same way a hosted connection sends it, so calls are metered and billed exactly as they are there.

It lists only this pack's tools by default. Set PIPEWORX_META_TOOLS=1 to also list ask_pipeworx and the other gateway-wide tools.

Behind an HTTPS proxy: Node's built-in fetch does not read HTTPS_PROXY by default. Newer Node releases honour it when NODE_USE_ENV_PROXY=1 is set; check your Node version's documentation.

Using with ask_pipeworx

Instead of calling tools directly, you can ask questions in plain English — this works on the pack endpoint above as well as on the full gateway:

ask_pipeworx({ question: "your question about Polymarket Us data" })

The gateway picks the right tool and fills the arguments automatically.

More

• Docs and guides
• pipeworx.io

License

MIT