Agent skill · software engineering · anthropics
build-mcpb
This skill should be used when the user wants to "package an MCP server", "bundle an MCP", "make an MCPB", "ship a local MCP server", "distribute a local MCP", discusses ".mcpb files", mentions bundling a Node or Python runtime with their MCP server, or needs an MCP server that interacts with the local filesystem, desktop apps, or OS and must be installable without the user having Node/Python set up.
Why this skill is useful
Adds a complete packaging script for creating MCPB bundles that include runtime dependencies, which the AI cannot generate on its own.
What it needs
Requires node installed locally. About 4k tokens when loaded. Last updated 2026-08-07. 33,212 stars on the source repository.
What this skill does
Build an MCPB (Bundled Local MCP Server) MCPB is a local MCP server packaged with its runtime. The user installs one file; it runs without needing Node, Python, or any toolchain on their machine. It's the sanctioned way to distribute local MCP servers. MCPB is the secondary distribution path. Anthropic recommends remote MCP servers for directory listing — see https://claude.com/docs/connectors/building/what-to-build. Use MCPB when the server must run on the user's machine — reading local files, driving a desktop app, talking to localhost services, OS-level APIs. If your server only hits cloud APIs, you almost certainly want a remote HTTP server instead (see build-mcp-server). Don't pay the MCPB packaging tax for something that could be a URL. --- What an MCPB bundle contains The host reads manifest.json, launches server.mcpconfig.command as a stdio MCP server, and pipes messages. From your code's perspective it's identical to a local stdio server — the only difference is packaging. --- Manifest server.type — node, python, or binary. Informational; the actual launch comes from mcpconfig. server.mcpconfig — the literal command/args/env to spawn. Use ${dirname} for bundle-relative paths and ${userconfig.<key>} to substitute install-time config. There's no auto-prefix — the env var names your server reads are exactly what you put in env. userconfig — install-time settings surfaced in the host's UI. type: "directory" renders a native folder picker. sensitive: true stores in OS keychain. See references/manifest-schema.md for all fields. --- Server code: same as local stdio The server itself is a standard stdio MCP server. Nothing MCPB-specific in the tool logic. Sandboxing is entirely your job. There is no manifest-level sandbox — the process runs with full user privileges. Validate paths, refuse to escape ROOT, allowlist spawns. See references/local-security.md. …
How to use it
Reference it in AdaL, Claude Code, Cursor or any coding agent — nothing to install:
@skills anthropics/build-mcpb