bb1/thunderbird-mcp

thunderbird-mcp

This repository contains a Thunderbird extension that exposes experimental APIs for accessing the Thunderbird search index, managing the calendar, searching contacts, and sending mail. The extension also starts a small HTTP server (referred to as the MCP server) that exposes these capabilities using JSON-RPC 2.0 messages. MCP stands for Model Context Protocol; see https://modelcontextprotocol.io/specification/2025-06-18 for the specification.

Extension contents

extension/
├── background.js        - Starts the MCP server
├── manifest.json        - Extension manifest
├── search_index/
│   ├── api.mjs
│   └── schema.json
├── calendar/
│   ├── api.mjs
│   └── schema.json
└── contacts/
    ├── api.mjs
    └── schema.json

The experimental APIs integrate with Thunderbird's search index and calendar services and are usable from other scripts via the MCP server. They enable the following MCP tools:

• searchMessages – search the message index
• sendMail – compose and dispatch a mail
• listCalendars – list available calendars
• searchContacts – look up contacts the user interacted with

Loading the extension in Thunderbird

1. Open Thunderbird and navigate to Add-ons and Themes.
2. Use Debug Add-ons to load the extension directory as a temporary add-on.
3. The extension will start the MCP server on http://localhost:8765. Send JSON-RPC requests via POST /.
   • tools/list returns available tools
   • tools/call invokes one of the tools with arguments

The extension requires Thunderbird 102 or later.

Running tests

The repository includes a small test runner. After installing development dependencies, run:

npm test

The script downloads Thunderbird, launches the extension in headless mode using web-ext, and checks that the MCP server responds to tools/list.