MCPB (MCP Bundle)

MCPB — MCP Bundle — is a distribution format that packs an entire local MCP server into one file: the code, its dependencies, and a manifest describing how to run it. A desktop client like Claude Desktop can install the bundle with a click, the way a browser installs an extension.

The format began life as DXT (Desktop Extensions) before being renamed MCPB, so you'll still see the old name in older docs and tooling.

Installing a local MCP server traditionally means a terminal: have Node.js or Python installed, run an npx or uvx command, then hand-edit a JSON config file with exact paths and arguments. For developers that's a minor chore; for everyone else it's a wall.

An MCPB collapses all of that into open-file-and-confirm. Dependencies travel inside the bundle, the manifest tells the client how to launch the server, and any settings the server needs (API keys, folder paths) are collected through a UI the client renders from the manifest's declared configuration fields.

An .mcpb file is a zip archive. At its root sits a manifest.json declaring the server's name, version, entry point, runtime requirements, and user-configurable settings; alongside it lives the server code and its bundled dependencies — node_modules for a Node server, packaged libraries for Python.

Because dependencies are vendored in, the bundle runs without the user pre-installing a runtime toolchain — the central promise of the format.

MCPB targets non-technical desktop users; package registries target developers. If your audience configures Cursor and Claude Code by hand, an npm or PyPI package is lighter to maintain and composes with existing workflows. If your audience is Claude Desktop users who have never opened a terminal, a bundle removes the single biggest drop-off point in your install funnel.

These aren't exclusive. A server's registry manifest (server.json) can declare several package types at once — npm for developers, MCPB for desktop users, a remote endpoint for those who want nothing installed — and registries like Loomal's index list whichever distribution forms the author has published.

MCPB is a local, stdio-based distribution format, so it inherits local-server constraints: the server runs on the user's machine, updates require shipping a new bundle, and client support is concentrated in desktop apps — as of mid-2026, editor and framework clients generally still expect package or remote configuration. For monetized servers, remote hosting over Streamable HTTP remains the natural shape, since x402 payment gating happens at an endpoint you operate.