Nest Bridge

A local MCP bridge so your AI can read and write your end-to-end-encrypted Nest data (people, companies, tasks, events) while Nest's servers only ever see ciphertext.

The bridge runs on your machine. It unlocks your encryption key locally from your password, holds it in memory, and decrypts on read / encrypts on write right there. Nest never receives your password, your key, or your plaintext - only the already-encrypted blobs and your API key.

your AI  <--stdio MCP-->  nest-bridge (your machine)  <--HTTPS-->  nest.scales.baby
                          |  decrypts on read         |
                          |  encrypts on write        |  stores ciphertext only
                          |  holds the key in memory  |

Security model

• Your API key and your encryption password stay on your machine. You supply them at runtime as environment variables (or, for the Claude Desktop connector, into your OS keychain).
• The bridge fetches only your password-wrapped key (ciphertext plus the public salt) from Nest, derives your key locally with Argon2id, unwraps the key locally, and keeps it in memory.
• Reads decrypt locally. Writes encrypt locally. The server stores only the encrypted blob with the plaintext columns blanked. Nest never receives the key, the password, or your plaintext.
• The crypto is the same WebCrypto + Argon2id (hash-wasm) code the Nest web app uses, so reads and writes round-trip byte-for-byte with the browser. See src/crypto/.
• Your AI provider sees what it reads. "Nest can't read your data" is not the same as "no one but you" once you connect an AI: the model you connect (Claude, OpenAI, etc.) sees the decrypted content the bridge returns to it. That is the point of connecting an AI. Mint a read-only key if you do not want it to write.
• A read-only key cannot write; a full-control key can. The server enforces this independently of the bridge.

This repository contains only the bridge and the client-side crypto. There is no server code, no database, and no secrets here.

Mint a key in Nest

Open Nest then Settings then Connect your AI and create a key.

• Read-only (the default) lets your AI read your data.
• Full control also lets it create and update records.

Copy the key when it is shown (it appears once). It looks like nest_ab12cd34_....

Run it (npx)

NEST_API_KEY="nest_ab12cd34_..." \
NEST_PASSWORD="your-encryption-password" \
NEST_NON_INTERACTIVE=1 \
npx -y @scales-baby/nest-bridge

The bridge fetches your wrapped key, unwraps it locally, and starts an MCP server on stdio. Point any MCP client at the same command. (-y skips npm's install-confirm prompt so the launch can't hang.)

When you run the bridge manually in a real interactive terminal, you can omit NEST_PASSWORD and NEST_NON_INTERACTIVE; the bridge then prompts Nest encryption password: with hidden input. This hidden prompt only works in a terminal. An MCP-spawned server has no TTY, so when an AI launches the bridge the password must come from config or your OS keychain (see below), not a prompt.

Configuration (environment variables)

Var	Default	Notes
NEST_API_KEY	(required)	Your scoped key from Nest.
NEST_PASSWORD	(prompt)	Set it to run non-interactively; else prompted.
NEST_API_URL	https://nest.scales.baby	Override only to test against another instance.
NEST_NON_INTERACTIVE	(unset)	Set to 1 when launched by an app (no prompt).
NEST_READ_ONLY	(unset)	Set to 1 to force read-only locally.

If your account is not end-to-end encrypted, the bridge runs in pass-through mode and no password is needed.

Claude Desktop (one-click .mcpb)

Build the connector bundle, then double-click it (or drag it onto Claude Desktop):

npm install
npm run pack:mcpb     # produces dist/scales-nest.mcpb

Claude Desktop opens an install panel for "Nest by SCALES" and asks for your Nest API key and Nest encryption password. Both are marked sensitive, so Claude Desktop stores them in your OS keychain (macOS Keychain / Windows Credential Manager), not in a plain file. Leave Nest URL at its default and enable it.

Where your password lives (pick one):

• Claude Desktop .mcpb (recommended): stores your password in the OS keychain.
• claude mcp add (below): stores it in your local Claude config (~/.claude.json), and the command line lands in your shell history. That is local-only, but prefer the .mcpb if you want it in the keychain.

Per-AI config snippets

Claude Code (CLI):

claude mcp add nest \
  --env NEST_API_KEY=nest_ab12cd34_... \
  --env NEST_PASSWORD=your-encryption-password \
  --env NEST_NON_INTERACTIVE=1 \
  -- npx -y @scales-baby/nest-bridge

After adding, reload so the tools appear: run claude --continue to resume the current session and load the MCP.

OpenAI / any stdio MCP client (JSON):

{
  "command": "npx",
  "args": ["-y", "@scales-baby/nest-bridge"],
  "env": {
    "NEST_API_KEY": "nest_ab12cd34_...",
    "NEST_PASSWORD": "your-encryption-password",
    "NEST_NON_INTERACTIVE": "1"
  }
}

Note: OpenAI's remote / hosted MCP is metadata-only on encrypted accounts. Only the local bridge returns decrypted content, because decryption happens on your machine.

Tools

People, Companies, Tasks, Events, each with list_*, get_*, search_*, create_*, update_*, plus complete_task and get_digest. 22 tools in all. Notes ride on the person / company / task / event they belong to.

• Reads fetch ciphertext from Nest, decrypt locally, return plaintext to your AI.
• Writes take your AI's plaintext, encrypt locally, send ciphertext to Nest.

If you minted a read-only key, the write tools politely decline (and Nest enforces it on the server too).

Build from source

git clone https://github.com/scales-baby/nest-bridge.git
cd nest-bridge
npm install
npm run build        # tsc → dist/
npm test             # crypto round-trip proof
npm start            # run the built bridge (needs the env above)

License

MIT. See LICENSE.