mcp-hey Server

mcp-hey

A local Model Context Protocol (MCP) server that gives Claude read/write access to your Hey.com inbox via reverse-engineered web APIs.

mcp-hey has two moving parts: a Bun/TypeScript MCP server that exposes Hey tools over stdio, and a small Python helper that uses the system webview to capture session cookies at login. Everything runs locally — no cloud relay, no credentials stored, just session cookies on disk.

Warning — unofficial API. Hey.com does not publish a public API; mcp-hey reverse-engineers its web endpoints and pairs them with browser-identical HTTP requests. Things can break without notice. The current documented surface lives in docs/API.md.

Features

Read emails from Imbox, Feed, Paper Trail, Set Aside, Reply Later, Drafts, Trash, and Spam
Download attachments and parse calendar invites from emails
Send and reply to email threads
Search emails across boxes
Organise mail (set aside, reply later, screen in/out, bubble up)
Local SQLite cache for faster repeated reads and full-text search
Lightweight — around 30 MB idle memory
Browser-identical headers and TLS posture to avoid detection
Runs entirely on your machine; stdio transport with no network exposure

Setup

Prerequisites

Bun 1.1 or later
Python 3.10 or later (plus UV if you want to follow the Python tooling in CLAUDE.md)
A Hey.com account
Platform: developed and tested on macOS and Linux. Windows users will likely need WSL — pywebview's Windows backend is not currently exercised.

Installation

Clone this repository

git clone https://github.com/Sealjay/mcp-hey.git
cd mcp-hey

Install dependencies

bun install
uv pip install -r auth/requirements.txt

First run — authenticate
```
bun run dev
```
1. A system webview opens with Hey.com's login page. Log in normally.
2. The helper captures session cookies to data/hey-cookies.json (permissions 600) and exits.
3. Press Ctrl+C — your MCP client will launch its own server instance from here on.
4. Subsequent runs reuse the stored session until it expires.

MCP client configuration

All clients below use the same command/args shape. On macOS, you'll almost certainly need the absolute path to bun — see macOS: bun PATH below.

Claude Code

The quickest route is the CLI:

claude mcp add --transport stdio hey --scope user -- bun run /absolute/path/to/mcp-hey/src/index.ts

The server is available immediately in the current session.

Alternatively, add to .mcp.json at your project root (or ~/.claude.json for a user-scoped server):

{
  "mcpServers": {
    "hey": {
      "type": "stdio",
      "command": "bun",
      "args": ["run", "/absolute/path/to/mcp-hey/src/index.ts"]
    }
  }
}

If you edit the file directly, restart the Claude Code session to pick it up.

Claude Desktop

Add to ~/Library/Application Support/Claude/claude_desktop_config.json (macOS):

{
  "mcpServers": {
    "hey": {
      "command": "bun",
      "args": ["run", "/absolute/path/to/mcp-hey/src/index.ts"]
    }
  }
}

Restart Claude Desktop. You should see hey listed as an available integration.

Cursor

Add to ~/.cursor/mcp.json:

{
  "mcpServers": {
    "hey": {
      "command": "bun",
      "args": ["run", "/absolute/path/to/mcp-hey/src/index.ts"]
    }
  }
}

Restart Cursor.

Docker

A Dockerfile is included for containerised deployments and Glama compatibility.

Build the image:

docker build -t mcp-hey .

Smoke-test the server (should return a JSON-RPC response listing available tools):

printf '{"jsonrpc":"2.0","id":1,"method":"tools/list"}\n' | docker run -i mcp-hey

Note: The Docker image runs the MCP server only. The Python auth helper and webview login are not available inside the container. You must provide pre-existing session cookies via a volume mount to data/hey-cookies.json for authenticated operations.

macOS: `bun` PATH

GUI apps (Claude Desktop, Cursor) and shells launched by Claude Code don't always inherit the PATH from your interactive terminal, so a Homebrew-installed bun may fail with spawn bun ENOENT or simply never connect. Fix by using the absolute path to bun in command:

Apple Silicon Homebrew — /opt/homebrew/bin/bun
Intel Homebrew — /usr/local/bin/bun
Manual install — run which bun in your terminal to find it

Example:

{
  "mcpServers": {
    "hey": {
      "command": "/opt/homebrew/bin/bun",
      "args": ["run", "/absolute/path/to/mcp-hey/src/index.ts"]
    }
  }
}

Architecture

Component	Description
MCP server	Bun/TypeScript, stdio transport, ~30 MB idle memory
Auth helper	Python/pywebview, spawns on-demand for login via system webview
Cache	Local SQLite store for messages, threads, and search index
Communication	File-based session sharing via `data/hey-cookies.json`

Data flow

MCP client (Claude Code, Claude Desktop, Cursor, etc.) launches bun run src/index.ts over stdio.
On startup the server validates data/hey-cookies.json. If missing or expired it spawns auth/hey-auth.py, which opens Hey in a system webview and writes fresh cookies.
Tool calls hit Hey.com directly with browser-realistic headers; responses are parsed (HTML via node-html-parser) and cached in SQLite.
Write operations fetch a fresh CSRF token before submitting.

Project structure

mcp-hey/
  src/
    index.ts           # MCP server entry point
    hey-client.ts      # HTTP client with cookie injection
    session.ts         # Session management and validation
    errors.ts          # Error classes and sanitisation
    cache/             # SQLite cache (db, schema, messages, search)
    tools/             # MCP tool implementations
      read.ts          # Reading and listing
      send.ts          # Send, reply, forward
      organise.ts      # Triage, labels, bubble up, etc.
      http-helpers.ts  # Shared CSRF retry and endpoint fallback
      attachments.ts   # Download attachments, parse calendar invites
    __tests__/         # Test suites
  auth/
    hey-auth.py        # Python auth helper (pywebview)
    requirements.txt
  data/
    hey-cookies.json   # Session storage (gitignored, chmod 600)
  docs/
    API.md             # Hey.com API surface documentation
    TOOLS.md           # MCP tool reference (34 tools)
    hey-features-doc.md  # Hey.com feature mapping

Available tools

34 tools grouped by function. See docs/TOOLS.md for parameters, return shapes, and error behaviour.

Category	Tools
Read	`hey_list_emails` (imbox, feed, paper_trail, trash, spam, drafts), `hey_imbox_summary`, `hey_list_set_aside`, `hey_list_reply_later`, `hey_list_screener`, `hey_read_email`, `hey_download_attachment`, `hey_get_calendar_invite`
Labels & Collections	`hey_list_labels`, `hey_list_label_emails`, `hey_label`, `hey_list_collections`, `hey_list_collection_emails`, `hey_collection`
Send	`hey_send_email`, `hey_reply`, `hey_forward`
Triage	`hey_set_aside`, `hey_unset_aside`, `hey_reply_later`, `hey_remove_reply_later`, `hey_move_to`, `hey_set_status`, `hey_mark_unseen`, `hey_mark_seen`, `hey_read_status`, `hey_thread_mute`
Bubble up	`hey_bubble_up`, `hey_bubble_up_if_no_reply`, `hey_pop_bubble`
Screener	`hey_screen`, `hey_screen_by_id`
Search	`hey_search`
Cache	`hey_cache_status`

Privacy and security

No credentials are ever stored — only session cookies, written with 600 permissions.
Authentication happens entirely inside Hey's own login page (system webview).
All data stays on your machine. No telemetry is emitted by this project.
MCP uses stdio transport — the server never opens a network listener.
Session validity is checked on startup and before sensitive operations.

See SECURITY.md for how to report vulnerabilities.

Limitations

Prompt-injection risk: as with many MCP servers, this one is subject to the lethal trifecta. A malicious email arriving in your inbox could attempt to instruct Claude to exfiltrate other messages. Treat the tool surface accordingly and review risky actions before approving them.
Unofficial API: Hey.com's frontend can change without notice and break things. Expect occasional breakage and check docs/API.md for known deltas.
No real-time notifications: polling only.
Attachment uploads are not yet supported.
Single account per MCP server instance.
Account risk: aggressive or abnormal access patterns could in theory trigger Hey's anti-abuse systems. The server respects x-ratelimit headers and backs off exponentially, but there are no guarantees.
English UI only: the server parses Hey.com's HTML responses and matches English-language strings (e.g. "You ignored this thread", label names, button text). It will not work correctly if Hey.com is set to a non-English locale.

Troubleshooting

Auth webview does not open — confirm Python 3.10+ is on PATH and uv pip install -r auth/requirements.txt succeeded. On Linux ensure a webview backend is available (python -c "import webview" should not error).
401/403 responses after weeks of use — your Hey session has expired. Delete data/hey-cookies.json and run bun run dev again to re-auth.
Rate limits (429) — the client respects x-ratelimit headers and backs off. If you see sustained 429s, reduce concurrent tool use or wait a few minutes.
MCP client can't launch the server — args must be an absolute path, not relative. If bun itself fails with spawn bun ENOENT, see macOS: bun PATH.
Cookie name changed — Hey has renamed session cookies before (e.g. _hey_session → session_token, see docs/API.md changelog). If auth silently fails after a Hey update, capture fresh cookies and compare.

Contributing

Contributions welcome via pull request. Please:

Use conventional commits (feat, fix, docs, refactor, test, perf, cicd, revert, WIP).
Run bun run format and bun run lint before pushing (powered by Biome).
Ensure bun test passes.
Update docs/API.md if you discover or change any Hey.com API behaviour.

See CLAUDE.md for the full development workflow.

Licence

MIT Licence — see LICENCE.

Documentation