MCP Bundles (MCPB)
The .mcpb format and a CLI that package a local MCP server into one file installable in Claude Desktop with one click
Install
npm install -g @anthropic-ai/mcpbThen in the server folder: mcpb init and mcpb pack.
This is third-party code. Review the repository files before installing.
What it does
An MCPB is a zip archive holding a local MCP server and a manifest.json describing the server, its parameters and capabilities. The mcpb CLI helps create the manifest with init and build the archive with pack. The repository also holds the manifest spec, example bundles for Node.js, Python and binaries, and the code Claude for macOS and Windows uses to verify and load bundles. The project was previously called DXT; .dxt files are now .mcpb.
Who it is for. For authors of local MCP servers who want to ship them to users without manual config editing.
Good fit when
- You need to give non-technical users a local MCP server
- You want server parameters and secrets configured through the app UI
- You build a desktop app and want to support bundle installs
Not a fit when
- The server is remote and runs over HTTP
- Users work in CLI agents where a single command connects the server more easily
Example request
Package my MCP server as an MCPB bundle: create manifest.json per the spec and build the .mcpbLimitations
Python bundles cannot portably include compiled dependencies, so the authors recommend Node.js servers or the uv type. The main consumer of the format today is Claude for macOS and Windows. The CLI itself runs locally and needs no external services.
How to disable. Uninstall the CLI with npm uninstall -g @anthropic-ai/mcpb. An installed bundle is disabled in Claude Desktop's extension settings.
Security check
- The CLI only builds an archive from local files
README in short
The README explains the bundle format by comparing it to browser and editor extensions and lists the repository's three parts: the spec, the CLI and Claude Desktop's loading code. It covers init and pack, folder layouts for Node.js, Python and binary servers, and how to package dependencies. It includes a ready prompt for an agent building a bundle. New code is Apache 2.0, older code MIT.
FAQ
How does MCPB differ from DXT?
It is the same project renamed: the dxt CLI became mcpb and .dxt files became .mcpb.
Which language should the server use?
The authors recommend Node.js because it ships with Claude Desktop, so users need no Python install.
Related
Open-source personal AI assistant on your own machine: answers in Telegram, Slack, Discord and WhatsApp, extended with skills and plugins
A self-improving agent from Nous Research with a TUI, messaging gateway, cron jobs and skills it writes itself
An open source coding agent for the terminal and desktop with build and plan modes
Open prompt library with a Claude Code plugin, MCP server and CLI: search, fetch and improve prompts and skills from an agent