What is an MCP Bundle?

If you’ve tried to share an MCP server with someone, you know the pain: clone the repo, install the right Python or Node version, run dependency installation, configure paths, hope nothing breaks. MCPB solves this.

The Problem with MCP Servers Today

MCP (Model Context Protocol) is powerful. It lets AI assistants like Claude interact with external tools and data. But distributing MCP servers is a mess:

# The typical "installation" experience
git clone https://github.com/someone/cool-mcp-server
cd cool-mcp-server
python -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt
# Now figure out how to configure Claude Desktop...
# Hope the Python version is compatible...
# Debug why it's not working...

This friction kills adoption. Great tools sit unused because installation is too hard.

What MCPB Does

MCPB (MCP Bundle) is a packaging format that bundles an MCP server with everything it needs to run:

my-server.mcpb (a zip file)
├── manifest.json     # Metadata + how to run it
├── src/              # Your server code
└── deps/             # ALL dependencies, vendored

One file. Everything included. No installation steps.

One Command

With MCPB + mpak:

# That's it. That's the whole installation.
mpak bundle run @nimblebraininc/postgres-mcp

The CLI:

1. Downloads the .mcpb file from the registry
2. Extracts it locally
3. Runs the server with the bundled dependencies

No Python version conflicts. No missing dependencies. No path configuration. It just works.

How It Works

1. Dependencies Are Vendored

When you build a bundle, all dependencies are copied into the bundle itself:

Server Type	Dependencies Location
Python	deps/ directory (via pip install --target)
Node.js	node_modules/ (via npm install)
Binary	The compiled executable itself

The server runs using these bundled dependencies, not whatever’s installed on the user’s system.

2. The Manifest Describes Everything

The manifest.json tells mpak how to run the server:

{
  "name": "@yourorg/postgres-mcp",
  "version": "1.0.0",
  "description": "Query PostgreSQL databases",
  "server": {
    "type": "python",
    "mcp_config": {
      "command": "python",
      "args": ["-m", "postgres_mcp.server"],
      "env": {
        "PYTHONPATH": "${__dirname}/deps"
      }
    }
  }
}

The ${__dirname} variable resolves to wherever the bundle is extracted, so paths always work.

3. Platform-Specific When Needed

Pure Python and Node.js bundles work everywhere. But if your server has native dependencies (C extensions, Rust bindings), you can build platform-specific bundles:

@yourorg/postgres-mcp@1.0.0
├── darwin-arm64.mcpb   # macOS Apple Silicon
├── darwin-x64.mcpb     # macOS Intel
├── linux-x64.mcpb      # Linux x64
└── linux-arm64.mcpb    # Linux ARM

mpak automatically downloads the right one for the user’s system.

Why This Matters

For Users

• Zero friction - mpak bundle run @org/server and you’re done
• Reproducible - Same bundle, same behavior, every time
• No conflicts - Bundled dependencies don’t interfere with your system

For Authors

• Ship once, run everywhere - Build it, publish it, forget about “works on my machine”
• No support burden - Users don’t file issues about installation problems
• Version control - Users can pin to specific versions

For the Ecosystem

• Discoverability - Search mpak.dev to find servers
• Trust - Provenance tracking shows exactly where bundles came from
• Standards - One format means tools can build on top of it

MCPB vs. Other Approaches

Approach	Pros	Cons
Git clone + install	Familiar	Dependency hell, version conflicts
Docker	Isolated	Heavy, requires Docker, overkill for CLI tools
System packages	Native	Platform-specific, complex publishing
MCPB	Lightweight, portable, bundled deps	Requires mpak CLI

MCPB hits the sweet spot: lightweight like a script, reliable like a container.

The Specification

MCPB is an open specification maintained at github.com/modelcontextprotocol/mcpb.

Key points:

• .mcpb files are zip archives
• manifest.json is required at the root
• Dependencies are vendored (not referenced)
• Platform metadata enables multi-platform distribution

mpak is one implementation of the MCPB spec. Others can build compatible tools.

Try It

See MCPB in action:

# Install the CLI
npm install -g @nimblebrain/mpak

# Search for a server
mpak bundle search echo

# Run it instantly
mpak bundle run @nimblebraininc/echo

No setup. No configuration. Just works.

Next Steps

Quickstart Run your first MCP server in 2 minutes

Migrate Your MCP Server Publish an existing MCP server to mpak