mcp-freestyle

A Model Context Protocol server that reads data from a FreeStyle glucose sensor.

Requirements

This server reads your data from Abbott's cloud, so it only works if your data already gets there. You need all of the following:

• A FreeStyle sensor read by the LibreLink app on a phone. If you use a standalone FreeStyle reader instead, nothing is uploaded continuously and this server cannot help you.

• LibreLinkUp sharing set up from that LibreLink app to a follower account. The server signs in as the follower.

• Node.js ≥ 20, and a working OS keychain (macOS Keychain, Windows Credential Manager, or libsecret on Linux).

The server talks to the unofficial LibreLinkUp / LibreView API, which is not affiliated with or supported by Abbott. It can stop working without notice. See docs/decisions/0002-data-source-librelinkup.md.

Related MCP server: mcp-server-dexcom-health

Quickstart

1. Install

npm install -g mcp-freestyle

Or from a clone, if you'd rather read the code first:

git clone https://github.com/lozit/mcp-freestyle.git && cd mcp-freestyle
npm install && npm run build

2. Log in once

npm run login          # from a clone
mcp-freestyle-login    # if installed globally

You're prompted for your LibreLinkUp follower e-mail and password. The password is verified by actually authenticating — if it's wrong, or sharing isn't set up, you find out now rather than at the first question you ask Claude. It is then stored in your OS keychain, never in a config file.

The token upstream issues is not stored. It lives ~180 days with no revocation path, so keeping it around would be the bigger risk; the server re-authenticates instead.

At the end, login offers to wire the server into Claude Desktop in one step.

3. Hook it up to Claude

Claude Desktop — one command:

mcp-freestyle-install

It merges an entry into ~/Library/Application Support/Claude/claude_desktop_config.json (%APPDATA%\Claude\… on Windows) using absolute paths, backing up any existing config first and leaving your other servers untouched. It refuses to overwrite a config it can't parse. Quit Claude Desktop fully (⌘Q) and relaunch.

Claude Code:

mcp-freestyle-install code   # prints the exact `claude mcp add` command

The written entry contains only your e-mail — an identifier, not a secret. That is the point of the keychain step: a config file that gets synced, backed up, or pasted into a bug report never holds a credential.

To remove the stored password: mcp-freestyle-logout.

Configuration

Tools

Upstream holds only ~12 hours of detailed data. Longer horizons are a deferred milestone, not a limitation of these tools.

Development

npm test          # Node's built-in test runner — no build step needed
npm run typecheck # strict TypeScript, the project's only lint gate
npm run build     # emits dist/

Usage

Once connected, ask in plain language:

What's my glucose right now?

How has my time in range been today?

Show me the last 6 hours.

The answers carry the instant each reading was actually taken, the range the data actually covered, and any collection gaps — so a reply about "today" says how much of today it could see. If you ask for more than upstream holds, it tells you what it got instead of quietly answering over less.

Not a substitute for your reader or your app. This is informational only — see the disclaimer above.

Project structure

• README.md — this file

• CLAUDE.md — instructions for Claude Code

• docs/ — project documentation (architecture, decisions, learnings)

• intake/ — upstream notes and raw specs

• docs/media/ — visual assets

Documentation

• Vision: docs/VISION.md

• Architecture: docs/ARCHITECTURE.md

• Decisions: docs/decisions/

• Learnings: docs/LEARNINGS.md

• Glossary: docs/GLOSSARY.md

• Data model: docs/DATA_MODEL.md

• Security & privacy: docs/SECURITY.md

• Roadmap: docs/ROADMAP.md

Disclaimer

Not a medical device. This project is informational only. Do not use its output to make any treatment decision (dosing, correction, therapy adjustment). Always rely on your official reader/app and your care team.

Contributing

Issues and pull requests are welcome — especially from anyone who can help map the TrendArrow values (see below), or who hits a LibreLinkUp region or payload shape this hasn't seen.

npm test          # Node's built-in runner, no network — `fetch` is injectable
npm run typecheck # strict TypeScript, the project's only lint gate

One rule that is not negotiable: never commit a real glucose reading, sensor serial, account identifier, or credential — not in a fixture, not in an issue, not in a screenshot. Tests use synthetic fixtures only. A value paired with a timestamp is a health measurement even with no name attached.

Design decisions live in docs/decisions/ and the verified upstream contract in docs/ARCHITECTURE.md. Read those before changing how readings are fetched or aggregated — several non-obvious upstream behaviours are documented there because they cost real debugging to find.

Known gaps

• TrendArrow is not translated. Upstream sends an integer; its mapping is undocumented and has only been observed at one value. It is passed through as raw_trend_arrow rather than guessed at — a confidently wrong arrow is worse than none.

• ~12 hours of history, maximum. Upstream ignores any longer request. See ADR 0003 for the long-term plan.

Security

Report vulnerabilities privately to guillaume.ferrari@protonmail.com — see docs/SECURITY.md.

License

MIT © Guillaume Ferrari