build-mcpb

name	build-mcpb
description	This skill should be used when the user wants to package an MCP server, bundle a local MCP server, make an MCPB, ship a local server without a separate runtime install, or distribute a local filesystem, desktop, hardware, or localhost integration.
version	0.2.0

Build an MCPB

Provenance: Forked from anthropics/claude-plugins-official/plugins/mcp-server-dev under Apache-2.0. Significant changes: updated for the current MCPB 0.4 schema and modern-vs-legacy protocol handling. See ../THIRD-PARTY-NOTICES.md.

MCPB packages a local MCP server and its runtime as one installable archive. Choose it only when code must execute on the user's machine: local files, hardware, desktop automation, or localhost services. A cloud-API wrapper should normally be a remote HTTP server.

MCPB does not change MCP semantics

MCPB is distribution, not a protocol mode. Its server speaks stdio. The removal of initialize affects modern stdio as well as HTTP; do not write a new server or test fixture that assumes an initialization exchange.

A TypeScript v2 stdio server uses the v2 factory/server API and serveStdio. It may deliberately serve legacy clients too, but that is a dual-era decision—not a reason to hardcode initialize. See build-mcp-server/references/dual-era.md.

HTTP session removal does not alter the process-level fact that a stdio server is long-lived. Still avoid hiding durable application state in a connection object; use explicit state handles and authorization checks.

Manifest 0.4

The current MCPB source schema declares manifest_version: "0.4". Version 0.4 adds the uv Python runtime type.

{
  "$schema": "https://raw.githubusercontent.com/modelcontextprotocol/mcpb/main/schemas/mcpb-manifest-v0.4.schema.json",
  "manifest_version": "0.4",
  "name": "local-files",
  "version": "0.1.0",
  "description": "Read and search files under a selected local directory.",
  "author": { "name": "Your Name" },
  "server": {
    "type": "node",
    "entry_point": "server/index.js",
    "mcp_config": {
      "command": "node",
      "args": ["${__dirname}/server/index.js"],
      "env": {   
    
  
   
     
       
       
       
       
    
  
        

server.type is one of node, python, binary, or uv. mcp_config is the literal process command, arguments, and environment. There is no automatic environment-variable prefix and no manifest permission sandbox.

Build a defensible local server

1. Register narrow, single-purpose tools; separate reads from writes.
2. Resolve every input path and enforce containment below an approved root.
3. Construct child-process arguments as arrays; never concatenate shell input.
4. Keep user configuration, tokens, and runtime diagnostics out of model-visible output.
5. Make destructive behavior visible with tool annotations and explicit confirmation.

roots/list is a deprecated legacy feature, not a prerequisite for local-file safety. Use an install-time directory selection or an explicit, validated path capability instead.

Package and smoke-test

npx --yes @anthropic-ai/mcpb@2.1.2 validate manifest.json
npx --yes @anthropic-ai/mcpb@2.1.2 pack . inventory.mcpb

Run the packed server on a machine without the development toolchain. Exercise its stdio path with the intended host or Inspector, then install the resulting .mcpb in the target desktop host.

C# alternative

For C# servers, Microsoft also supports tool-style local distribution through PackAsTool and dnx. This can be a better fit for .NET-centric organizations that control the .NET runtime, while MCPB remains the all-in-one bundle path. Route to build-mcp-server-dotnet for its packaging decision tree.

References

• references/manifest-schema.md — full manifest fields and 0.4 schema details
• references/local-security.md — containment, process safety, and least privilege
• references/versions.md — version ledger and verification commands