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What Is Modern Web Guidance

When to Use

Reach for this reference when you need to understand what Modern Web Guidance is before deciding whether to install it — or when someone asks "is this an MCP server?" The short answer: it is not an MCP server.

Decision

Skill vs. MCP — the distinction that matters:

Agent Skill MCP Server
What it is A SKILL.md instruction file added to the agent's context A running server process exposing tools via the Model Context Protocol
How it activates Agent reads the skill instructions and calls a CLI Agent calls server-hosted tool functions via JSON-RPC
Network required No — the CLI runs fully offline (TensorFlow.js local embeddings) Yes — requires a running server process
Modern Web Guidance Yes — it is this No — MWG does not ship an MCP server

Two skill packs (selectable via --choose flag):

Skill pack System-prompt overhead Coverage
modern-web-guidance ~234 tokens Modern browser APIs, CSS, forms, passkeys, built-in AI, privacy, WebMCP
chrome-extensions ~181 tokens Manifest V3, background workers, Chrome Web Store

How it works end-to-end: 1. The skill is installed into your agent (via a plugin or CLI) 2. On a relevant web task, the agent runs modern-web-guidance search "<query>" — offline, no API keys 3. The agent runs modern-web-guidance retrieve <guide-id> to pull the guide into context 4. The agent uses that guide to generate production-quality, modern web code

What problems it solves: - LLMs default to legacy patterns because training data contains vast amounts of older code - Models frequently misuse modern APIs they technically know exist - Models lack Baseline awareness — they recommend patterns without checking browser support

Coverage: 102 modern web features across CSS/Layout, HTML/DOM, JS/APIs; 128 real-world use cases.

Common Mistakes

  • Assuming MWG is an MCP server — it is not; no MCP server is included or required
  • Installing both skill packs when you only need modern-web-guidance — use --choose to minimize token overhead if Chrome extension development is not in scope
  • Expecting MWG to replace deep framework knowledge — it covers the web platform layer, not Drupal, React, etc.

See Also