Check npm package bundle sizes, dependencies, and tree-shakeability via bundlephobia-mcp (npx)

Recipe: check npm package bundle size via bundlephobia-mcp

Server: [email protected] (npm, stdio) Launch: npx -y [email protected] Auth: none required Tools: 4 — get_npm_package_info, get_npm_package_info_history, search, fetch

What it does

Wraps the Bundlephobia API as an MCP stdio server. Query any npm package for:

• Minified + gzipped bundle size
• Dependency count and individual dependency sizes
• Tree-shakeability (hasSideEffects, hasJSModule, isModuleType)
• Per-asset breakdown (main bundle, CSS, etc.)
• Version history of all the above

MCP handshake

→ initialize(protocolVersion="2024-11-05")
← serverInfo: {name:"bundlephobia-mcp", version:"0.2.9"}
← capabilities: {tools:{listChanged:true}}

→ tools/list
← 4 tools: get_npm_package_info, get_npm_package_info_history, search, fetch

Real execution: getnpmpackage_info("react")

→ tools/call  name="get_npm_package_info"  arguments={"name":"react"}
← {
    isError: false,
    result: {
      name: "react",
      version: "19.2.7",
      size: 7593,          // 7.6 KB minified
      gzip: 2909,          // 2.9 KB gzipped
      dependencyCount: 0,
      dependencySizes: [{name:"react", approximateSize:7798}],
      hasJSModule: false,
      hasJSNext: false,
      hasSideEffects: true,
      isModuleType: false,
      scoped: false,
      description: "React is a JavaScript library for building user interfaces.",
      repository: "https://github.com/facebook/react.git",
      assets: [{name:"main", size:7593, gzip:2909, type:"js"}]
    }
  }

Response time: sub-second. The structured output includes both content[].text and structuredContent with the typed object.

When to use

• Before adding a dependency: check if the bundle impact is acceptable
• Comparing alternatives: get_npm_package_info on each candidate
• Tracking bloat over time: get_npm_package_info_history shows all versions
• fetch takes a pinned name@version string for exact version lookups

Gotchas

• The search tool description says "past information" but it's actually a package search (duplicated description from get_npm_package_info_history)
• hasSideEffects: true means the package is NOT tree-shakeable
• Asset sizes are in bytes, not kilobytes