@fileseal/send

fileseal-send (MCP server)

A standalone Model Context Protocol stdio server that wraps the FileSeal Secure Send API (/v1/sends). It encrypts files client-side (AES-GCM-256) before they ever reach FileSeal and exposes three tools to an MCP client (e.g. Claude).

This package is self-contained: it does not import from the FileSeal Next app. Its crypto (crypto.mjs) mirrors FileSeal's server-side attachment format byte-for-byte — a 12-byte IV followed by AES-GCM ciphertext, with the key base64url-encoded in the link fragment — so that ciphertext it produces decrypts on the FileSeal /receive/[id] page. That page fixes the format: a changed crypto.mjs produces links that will not open.

Tools

• secure_send — encrypt a file and create a send.
  • Inputs: filePath or (fileBase64 + filename + mimeType), recipientEmail?, deliveryMode ('link' default | 'email'), expiryHours? (1-168, default 48), message?, senderName?.
  • link mode (default, zero-knowledge for the file): the AES key is never sent to FileSeal; the tool returns the full share link with the key in its #k= fragment.
  • email mode: FileSeal emails the recipient a working link and stores the key server-side. Requires recipientEmail. Pass senderName too: without it the email says the files are from "Someone".
  • Not encrypted, in either mode: the file name, senderName and message. FileSeal stores them as plain text and anyone with the link can read them, so keep secrets out of message.
  • Limits: one file per call, up to 3 MB. The file travels inline as base64 in the request body, which is what caps it; FileSeal's own 10 MB per file is not reachable through this tool. Types: PDF, DOC, DOCX, TXT, JPG, PNG.
• send_status — { id } → status, expiry, download count, audit events. Only sends created with the same API key are visible.
• revoke_send — { id } → the link stops working immediately, and FileSeal attempts to delete the encrypted files from its servers.

Environment variables

Variable	Required	Default	Purpose
FILESEAL_API_KEY	yes	—	Bearer token sent as Authorization: Bearer <key> on every call. The server exits at startup if unset.
FILESEAL_API_BASE_URL	yes, in practice	http://localhost:3000	API origin: set it to https://fileseal.uk. The localhost default only suits developing FileSeal itself. Routes are <base>/v1/sends.

Running

No install needed — npx fetches and runs the latest published version:

FILESEAL_API_KEY=fsk_... \
FILESEAL_API_BASE_URL=https://fileseal.uk \
npx -y @fileseal/send

The server speaks MCP over stdio, so it's normally launched by an MCP client rather than run by hand.

Run from source

# from this package's directory
npm install
FILESEAL_API_KEY=fsk_... \
FILESEAL_API_BASE_URL=https://fileseal.uk \
node index.mjs

Wiring into Claude (.mcp.json)

{
  "mcpServers": {
    "fileseal-send": {
      "command": "npx",
      "args": ["-y", "@fileseal/send"],
      "env": {
        "FILESEAL_API_KEY": "fsk_your_api_key_here",
        "FILESEAL_API_BASE_URL": "https://fileseal.uk"
      }
    }
  }
}

The "fileseal-send" key is just the local server label; the npm package is @fileseal/send. To run a local checkout instead, point command/args at your copy of index.mjs.