Extension MCP Server

@kaptionai/mcp-extension

MCP server that lets AI assistants read and manage your WhatsApp conversations through the KaptionAI Chrome extension. Also supports WebMCP for zero-config browser-native AI tool discovery.

Claude / Cursor ──stdio──> mcp-whatsapp ──ws://localhost:7865──> KaptionAI Extension ──> WhatsApp Web
Browser AI Agent ──navigator.modelContext──> KaptionAI Extension ──> WhatsApp Web (WebMCP)

Setup

1. Install the extension

Install the KaptionAI Chrome Extension and enable the MCP bridge in settings.

2. Configure your AI tool

Claude Desktop

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

{
  "mcpServers": {
    "whatsapp": {
      "command": "npx",
      "args": ["-y", "@kaptionai/mcp-extension@latest"]
    }
  }
}

Claude Code

claude mcp add whatsapp -- npx -y @kaptionai/mcp-extension@latest

Cursor

Add to .cursor/mcp.json in your project or go to Settings > MCP Servers:

{
  "mcpServers": {
    "whatsapp": {
      "command": "npx",
      "args": ["-y", "@kaptionai/mcp-extension@latest"]
    }
  }
}

Windsurf

Add to ~/.codeium/windsurf/mcp_config.json:

{
  "mcpServers": {
    "whatsapp": {
      "command": "npx",
      "args": ["-y", "@kaptionai/mcp-extension@latest"]
    }
  }
}

VS Code (Copilot)

Add to .vscode/mcp.json in your project:

{
  "servers": {
    "whatsapp": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "@kaptionai/mcp-extension@latest"]
    }
  }
}

Or add to your VS Code settings.json:

{
  "mcp": {
    "servers": {
      "whatsapp": {
        "type": "stdio",
        "command": "npx",
        "args": ["-y", "@kaptionai/mcp-extension@latest"]
      }
    }
  }
}

Zed

Add to Zed settings (~/.config/zed/settings.json):

{
  "context_servers": {
    "whatsapp": {
      "command": {
        "path": "npx",
        "args": ["-y", "@kaptionai/mcp-extension@latest"]
      }
    }
  }
}

OpenAI Agents SDK (Python)

from agents import Agent
from agents.mcp import MCPServerStdio

whatsapp = MCPServerStdio(
    name="whatsapp",
    command="npx",
    args=["-y", "@kaptionai/mcp-extension@latest"],
)

agent = Agent(
    name="assistant",
    instructions="You can access WhatsApp conversations.",
    mcp_servers=[whatsapp],
)

Any MCP-compatible client

This package runs as a standard MCP server over stdio. To connect from any client:

npx -y @kaptionai/mcp-extension@latest

The server communicates via stdin/stdout using the MCP protocol. Point your client's MCP configuration to this command.

3. Open WhatsApp Web

Open web.whatsapp.com in Chrome or Edge. The extension will auto-connect to the MCP server.

Tools

query

Query WhatsApp data — conversations, contacts, messages, transcriptions, labels, and communities.

# List conversations
query {}

# Search everything
query { query: "meeting" }

# Unread only
query { unread: true }

# Look up a conversation with messages
query { id: "5511999887766@c.us" }

# Search contacts
query { query: "Alice", entity: "contacts" }

# List labels (Business accounts)
query { entity: "labels" }

# Filter by label
query { label: "Important" }

# List communities
query { entity: "communities" }

# Filter by community
query { community: "My Community" }

# Get session info
query { entity: "session" }

summarize_conversation

Generate a summary of a conversation.

manage_labels

Manage WhatsApp Business labels — add, remove, create, or delete labels.

manage_lists

Manage personal chat lists (custom lists). The personal account equivalent of Business labels — organize chats into custom categories.

# List all custom lists
manage_lists { action: "list" }

# Get a list with its chats
manage_lists { action: "get", name: "Family" }

# Create a new list
manage_lists { action: "create", name: "Work", conversation_id: "5511999887766@c.us" }

# Add a chat to a list
manage_lists { action: "add_chat", name: "Family", conversation_id: "5511999887766@c.us" }

# Remove a chat from a list
manage_lists { action: "remove_chat", name: "Family", conversation_id: "5511999887766@c.us" }

# Delete a list
manage_lists { action: "delete", name: "Old List" }

manage_chat

Manage chat state — archive, unarchive, mark as read/unread, pin, unpin, mute, unmute, set/clear draft messages.

# Archive a chat
manage_chat { action: "archive", conversation_id: "5511999887766@c.us" }

# Mark as read
manage_chat { action: "mark_read", conversation_id: "5511999887766@c.us" }

# Pin a chat (max 3)
manage_chat { action: "pin", conversation_id: "5511999887766@c.us" }

# Mute for 1 week
manage_chat { action: "mute", conversation_id: "5511999887766@c.us", mute_duration: "1w" }

# Set a draft message
manage_chat { action: "set_draft", conversation_id: "5511999887766@c.us", text: "Hey, I'll call you back" }

manage_reminders

Create and manage personal reminders. Stored in the cloud and delivered via the Kaption extension.

# List active reminders
manage_reminders { action: "list" }

# Create a reminder
manage_reminders { action: "create", title: "Follow up with client", datetime: "2026-03-07T14:00:00Z" }

# Complete a reminder
manage_reminders { action: "complete", id: "rem_abc123" }

# List all including completed
manage_reminders { action: "list", filter: "all" }

manage_scheduled_messages

Schedule messages to be sent automatically at a specific time, in one of two modes:

• bot (default) — sent from Kaption's WhatsApp number, not yours. Stored in Kaption's cloud and sent even when your computer is off. One-to-one chats only; one line, up to 800 characters.
• local ("From this computer") — sent from your own WhatsApp number, as you, while this computer and WhatsApp are open. Nothing leaves your device. Kaption keeps it within safe limits automatically (a few messages an hour and a day, minutes apart, only to chats where the other person has written, at most 3 a day to groups) and refuses what doesn't fit, with the reason. The only mode that can send to groups (ones you can post in and posted in within the last 30 days). Text only. A message whose time passes while the computer is off is marked missed, never sent late on its own.

The local mode has to be turned on by you in Kaption first (the "From this computer" option in the scheduling picker, after reading the limits and risks). An AI assistant can't turn it on; until you do, local requests are refused with (reason: no-consent). It is also rolled out gradually: where it isn't available yet, local requests are refused with (reason: flag-off) and the bot works as before.

# List pending messages of both modes (each one has a "mode")
manage_scheduled_messages { action: "list" }

# Schedule with the Kaption bot
manage_scheduled_messages { action: "create", message: "Hey, just following up!", datetime: "2026-03-07T09:00:00Z", conversation_id: "5511999887766@c.us" }

# Schedule from your own number, or to a group
manage_scheduled_messages { action: "create", mode: "local", message: "Running 10 min late", datetime: "2026-03-07T09:00:00-03:00", conversation_id: "5511999887766@c.us" }
manage_scheduled_messages { action: "create", mode: "local", message: "Standup moved to 10", datetime: "2026-03-07T09:00:00Z", conversation_id: "120363000000000000@g.us" }

# Cancel a scheduled message
manage_scheduled_messages { action: "delete", id: "msg_abc123" }
manage_scheduled_messages { action: "cancel", mode: "local", id: "3f2c…" }

download_media

Download and decrypt media from a message (images, videos, audio, documents).

Returns base64-encoded media data with mimetype, size, duration, and caption.

manage_notes

Read and write contact notes (WhatsApp Business).

call_recordings

Read WhatsApp call recordings made by the Kaption extension and their transcripts, with every word timed. Each recording names its conversation (the other person, or the group for a group call). Recordings of locked chats are never returned.

get_api_info

Get HTTP REST API connection info for programmatic access without MCP overhead. Returns URL, auth token, and available endpoints.

Multi-account support

Multiple WhatsApp accounts can be connected simultaneously (e.g. personal + business). Use target_session on any tool to route to a specific account. Query entity: "session" to see all connected accounts and their session IDs.

Multi-instance support

Multiple AI tools can share the same extension connection. The first instance starts a WebSocket hub; subsequent instances auto-detect the existing hub and relay through it. If the hub stops, a relay automatically promotes itself.

WebMCP support

Kaption is WebMCP-ready. On browsers that support the W3C WebMCP draft (navigator.modelContext, Chrome 146+), the extension automatically registers all tools with the browser's native AI tool registry. This means browser-based AI agents can discover and invoke Kaption tools without any MCP server or WebSocket connection — zero configuration.

When WebMCP is available, the extension registers tools prefixed with kaption_ (e.g. kaption_query, kaption_manage_chat) complete with JSON Schema input definitions and readOnlyHint annotations. The tools use the same handlers as the MCP server, so behavior is identical across both paths.

Security

• Localhost only — no cloud relay, no external connections
• No messages sent — AI assistants can read, organize, schedule, and draft, but never send messages directly
• Locked chats hidden — WhatsApp-locked conversations are excluded from all queries
• Feature-gated — MCP bridge must be explicitly enabled in the extension
• Business features gated — labels and notes require a WhatsApp Business account
• Rate limited — draft messages limited to 10 conversations per 5-minute window; write operations include random delays

License

BSL 1.1 — free to use, converts to MIT after 4 years.