Actually - What Markets Really Think

A Chrome extension and an MCP server that put prediction-market odds on top of the news you are already reading.

News tells you that "experts are concerned" or that "odds are rising". It rarely tells you a number. The number exists - on a prediction market, where people are betting their own money on the outcome. It just lives in another tab, and finding it means knowing such a market exists in the first place.

Actually closes that gap. Open an article, click the toolbar icon, and the extension matches the text against live Polymarket markets and shows the market's own probability. No account, no wallet, no signup.

What it does

• Matches an article to a market. A local embedding model (Xenova/all-MiniLM-L12-v2, ~33 MB) scores the article text against the cached market set, boosted by keyword and number overlap - numbers matter because the encoder is nearly blind to them, and "dip to $57,500" embeds almost identically to "reach $120,000".

• Runs on your device. Model and WASM runtime are bundled at build time - nothing is fetched from a CDN at install or runtime, and on the default settings the article text never leaves the machine.

• Reads non-English pages. They are translated to English before matching, using Chrome's own built-in Translator API (local, no network). Every Polymarket question is written in English, and the local model holds 86 Cyrillic tokens out of 30522 - an untranslated Russian headline embeds to noise. Translated, the same headline scores 0.53-0.71 against the market it is actually about, against a 0.35 floor.

  

• Trades, optionally. Connect any WalletConnect v2 wallet for limit and market orders, selling, cancelling resting orders, and a positions panel with cost basis and P&L. Keys and funds are never held by us.

• Serves agents too. The same capabilities are exposed over the Model Context Protocol: check_news, get_market, place_order, sell_order, cancel_order, get_positions.

Related MCP server: Polymarket Predictions MCP

How it fits together

extension/            Chrome MV3 extension (React popup, offscreen document)
extension/worker/     Cloudflare Worker - API proxy, rate limiting, market cache
packages/core/        Matching, pricing and Polymarket API logic, shared by both clients
packages/mcp-server/  MCP server, published to npm as actually-mcp-server
packages/market-cache-builder/   Cron job that precomputes the market embeddings

The heavy work lives in an offscreen document because MV3 service workers cannot run WASM, hold a WebSocket, or survive long enough to sign an order.

The market cache is 2000 open markets with precomputed embeddings, rebuilt every two hours. Selection blends three orderings - 24h volume, lifetime volume, and recency - because ranking by lifetime volume alone is the wrong shelf for a news tool: a market opened this morning under today's headline has no history and loses to a year-old election market every time.

The Worker exists so no client has to hold a credential. It proxies Polymarket's APIs, serves the precomputed cache, and acts as a remote signer for the relayer, so the builder credential stays on the server and never ships inside an extension.

Running it

npm install
npm run models:fetch -w extension   # bundle the embedding model
npm run build -w extension          # type-check + build to extension/dist

Load extension/dist as an unpacked extension in Chrome. Copy extension/.env.example to .env.local and fill it in first - the build bakes the Worker URL, the WalletConnect project id and the builder code.

npm test --workspaces               # 686 tests across four workspaces

Privacy

Discovery is free and needs no account. There are no content scripts: the page is read only when you click, and only the active tab. On the default settings (local embeddings, translation off-device) the article text does not leave your machine. Telemetry is opt-in and off by default.

Full policy: https://actually-api.sofiaseremeteva.workers.dev/privacy

Status

The extension is built and passing its release gates; the Chrome Web Store submission is in progress. actually-mcp-server is published on npm.

Redeeming a resolved position is in testing: builder authentication, neg-risk contract selection and the zero-balance guard are each verified against live services, but no redeem has yet been observed collecting funds end to end.

Trading is unavailable in several jurisdictions (US, GB, FR, BE, AU, SG, TH, TW, PL, and sanctioned countries), enforced Worker-side. Viewing odds works everywhere.

Actually does not provide financial advice.

License

See LICENSE.