Web Standards Specs

Remote MCP servers for searching and reading web standards specifications. Deployed as stateless Cloudflare Workers using the streamable-http transport.

Installation

OpenCode

Add to ~/.config/opencode/opencode.json (or your project's .opencode.json):

{
  "mcp": {
    "whatwg": {
      "type": "remote",
      "url": "https://whatwg-spec-mcp.jasnell.workers.dev/mcp",
      "enabled": true
    },
    "ietf": {
      "type": "remote",
      "url": "https://ietf-spec-mcp.jasnell.workers.dev/mcp",
      "enabled": true
    },
    "mdn": {
      "type": "remote",
      "url": "https://mdn-mcp.jasnell.workers.dev/mcp",
      "enabled": true
    },
    "wpt": {
      "type": "remote",
      "url": "https://wpt-mcp.jasnell.workers.dev/mcp",
      "enabled": true
    },
    "w3c": {
      "type": "remote",
      "url": "https://w3c-spec-mcp.jasnell.workers.dev/mcp",
      "enabled": true
    },
    "caniuse": {
      "type": "remote",
      "url": "https://caniuse-mcp.jasnell.workers.dev/mcp",
      "enabled": true
    },
    "nodejs": {
      "type": "remote",
      "url": "https://nodejs-mcp.jasnell.workers.dev/mcp",
      "enabled": true
    },
    "typescript": {
      "type": "remote",
      "url": "https://typescript-mcp.jasnell.workers.dev/mcp",
      "enabled": true
    }
  }
}

Claude Desktop

Add to ~/Library/Application Support/Claude/claude_desktop_config.json (macOS) or %APPDATA%\Claude\claude_desktop_config.json (Windows):

{
  "mcpServers": {
    "whatwg": {
      "url": "https://whatwg-spec-mcp.jasnell.workers.dev/mcp"
    },
    "ietf": {
      "url": "https://ietf-spec-mcp.jasnell.workers.dev/mcp"
    },
    "mdn": {
      "url": "https://mdn-mcp.jasnell.workers.dev/mcp"
    },
    "wpt": {
      "url": "https://wpt-mcp.jasnell.workers.dev/mcp"
    },
    "w3c": {
      "url": "https://w3c-spec-mcp.jasnell.workers.dev/mcp"
    },
    "caniuse": {
      "url": "https://caniuse-mcp.jasnell.workers.dev/mcp"
    },
    "nodejs": {
      "url": "https://nodejs-mcp.jasnell.workers.dev/mcp"
    },
    "typescript": {
      "url": "https://typescript-mcp.jasnell.workers.dev/mcp"
    }
  }
}

Claude Code

claude mcp add whatwg --transport http https://whatwg-spec-mcp.jasnell.workers.dev/mcp
claude mcp add ietf --transport http https://ietf-spec-mcp.jasnell.workers.dev/mcp
claude mcp add mdn --transport http https://mdn-mcp.jasnell.workers.dev/mcp
claude mcp add wpt --transport http https://wpt-mcp.jasnell.workers.dev/mcp
claude mcp add w3c --transport http https://w3c-spec-mcp.jasnell.workers.dev/mcp
claude mcp add caniuse --transport http https://caniuse-mcp.jasnell.workers.dev/mcp
claude mcp add nodejs --transport http https://nodejs-mcp.jasnell.workers.dev/mcp
claude mcp add typescript --transport http https://typescript-mcp.jasnell.workers.dev/mcp

Servers

WHATWG Spec MCP

Search and read WHATWG living standards — HTML, DOM, Fetch, URL, Streams, and 17 others.

Endpoint: https://whatwg-spec-mcp.jasnell.workers.dev/mcp

Tools

Tool	Description
list_standards	List all 22 WHATWG living standards with name, description, and URL. Optionally filter by search term.
search_all_standards	Search for sections across ALL WHATWG standards at once. Useful when you don't know which standard defines a concept (e.g., "structuredClone", "AbortSignal").
search_standard	Search within a specific standard for sections by title, ID, section number, or concept. Indexes both headings and <dfn> definitions.
search_spec_content	Full-text search within a standard's body text. Finds terms in algorithm steps and prose that don't have their own heading.
get_standard_toc	Browse the table of contents for a standard, with optional max_depth filtering for large specs like HTML.
get_standard_section	Fetch the full content of a section, converted to simplified markdown. Supports max_length for truncation.
search_issues	Search GitHub issues and pull requests across WHATWG repositories. Filter by type (issue, pr, or both).

Data Sources

Data	Source	Cache TTL
Standards list	spec.whatwg.org	24 hours
Spec section + dfn indexes	Individual spec pages	24 hours
HTML Standard sections	html.spec.whatwg.org/multipage/	24 hours
GitHub issues/PRs	GitHub Search API	15 minutes

---

IETF Spec MCP

Search and read IETF RFCs, Internet-Drafts, and working group information via the Datatracker API and RFC Editor.

Endpoint: https://ietf-spec-mcp.jasnell.workers.dev/mcp

Tools

Tool	Description
search_rfcs	Search published RFCs by title, keyword, or number. Searches both titles and abstracts, with whole-word scoring to reduce false positives.
get_rfc	Fetch metadata, abstract, and relationships (obsoletes, obsoleted-by, updates, updated-by) for an RFC. Warns when viewing an obsoleted document.
get_rfc_toc	Fetch the table of contents for an RFC, listing all sections with numbers, titles, and anchor IDs.
get_rfc_section	Fetch the full content of a specific RFC section, converted to simplified markdown. Supports max_length for truncation.
search_rfc_sections	Search within a single RFC for sections by title keyword, without reading the full TOC.
search_rfc_content	Full-text search within an RFC's body text. Finds where specific terms, algorithms, or concepts are discussed.
get_rfc_errata	Fetch published errata (post-publication corrections) for an RFC from the RFC Editor.
search_drafts	Search active Internet-Drafts by title or keyword.
get_draft	Fetch metadata and abstract for a specific Internet-Draft, with optional content excerpt.
list_working_groups	List or search active IETF working groups, optionally filtered by area.
get_working_group_documents	List the published RFCs and/or active Internet-Drafts belonging to a specific working group.
get_document_series	Look up which RFCs comprise a BCP, STD, or FYI document series (e.g., "BCP 56" → RFC 9205).

Data Sources

Data	Source	Cache TTL
RFC search/metadata	IETF Datatracker API	1 hour
RFC content (HTML)	rfc-editor.org/rfc/	24 hours
RFC relationships	Datatracker Related Documents API	1 hour
RFC errata	rfc-editor.org/errata/	24 hours
Internet-Draft search	Datatracker API	30 minutes
I-D content	ietf.org/archive/id/	1 hour
Working groups	Datatracker API	6 hours
BCP/STD series	Datatracker Related Documents API	24 hours

---

MDN Web Docs MCP

Search MDN Web Docs, fetch page content, extract code examples, and look up browser compatibility data from the @mdn/browser-compat-data project.

Endpoint: https://mdn-mcp.jasnell.workers.dev/mcp

Tools

Tool	Description
search_mdn	Search MDN articles by keyword — Web APIs, HTML elements, CSS properties, JavaScript features, and guides.
search_mdn_by_type	Search MDN filtered by content type (web-api, css, html, javascript, http, http-header, http-status, html-element, svg, guide).
get_mdn_page	Fetch a specific MDN page and return its content as simplified markdown (description, syntax, parameters, examples).
get_mdn_subpages	List child pages and navigation tree for an MDN page. Shows guides, interfaces, and related pages in hierarchy.
get_browser_compat	Fetch browser compatibility data for a feature (which browsers, from which version, with caveats). Resolves mirror entries to actual version numbers.
get_mdn_examples	Extract just the code examples from an MDN page. Useful when you already understand the concept and want usage patterns.
list_web_api_interfaces	List all members (constructor, properties, methods, events) of a Web API interface.
get_http_header	Fetch MDN documentation for a specific HTTP header — description, syntax, directives, examples.

Data Sources

Data	Source	Cache TTL
Search	MDN Search API	30 minutes
Page content	MDN Document API (JSON)	1 hour
Browser compat data	mdn/browser-compat-data (GitHub raw)	1 hour

---

Web Platform Tests MCP

Search, browse, and check results for web-platform-tests (WPT) — the shared conformance test suite used by all major browser engines. Test results from wpt.fyi.

Endpoint: https://wpt-mcp.jasnell.workers.dev/mcp

Tools

Tool	Description
search_wpt	Search WPT tests by name, path, or keyword. Returns matching tests with per-browser pass/fail results.
get_wpt_test	Fetch the source of a specific test file with extracted metadata (spec links, title, assertions).
list_wpt_directory	List test files and subdirectories in a WPT directory. Mirrors spec structure.
get_wpt_results	Fetch browser pass/fail results for a test path or directory from wpt.fyi. The interop signal.
get_wpt_interop_score	Compute cross-browser interoperability scores for a test directory — per-browser pass rates and an overall interop percentage.
get_wpt_diff	Compare test results between two browser runs. Shows newly passing, newly failing, and changed tests.
get_wpt_metadata	Fetch test metadata — spec references, title, and assertion summaries — without reading the full source.
search_wpt_by_spec	Find WPT tests that reference a specific spec URL. Scans test files via wpt.live for <link rel="help"> metadata.

Data Sources

Data	Source	Cache TTL
Test search + results	wpt.fyi API	30 min – 1 hour
Test source files	raw.githubusercontent.com / wpt.live	1 hour
Directory listings	wpt.live HTML directory pages	1 hour
Spec URL search	GitHub Code Search API / wpt.live scan	1 hour

---

W3C Specs MCP

Search and read W3C specifications, including all CSS Working Group editor drafts.

Endpoint: https://w3c-spec-mcp.jasnell.workers.dev/mcp

Tools

Tool	Description
search_w3c_specs	Search all 1,680 W3C specifications by title or keyword via the W3C API.
get_w3c_spec	Get metadata for a specific W3C spec by shortname — title, status, editor draft URL, TR URL.
list_css_specs	List all ~158 CSS editor drafts from drafts.csswg.org with last modified dates.
search_css_spec	Search sections within a specific CSS spec by heading title.
get_css_section	Fetch a specific section from a CSS spec, converted to simplified markdown.

Data Sources

Data	Source	Cache TTL
W3C spec catalog	W3C Specifications API	6 hours
CSS editor drafts index	drafts.csswg.org	24 hours
CSS spec content	drafts.csswg.org/{shortname}/	24 hours

---

Can I Use MCP

Look up browser support data and global usage percentages from caniuse.com.

Endpoint: https://caniuse-mcp.jasnell.workers.dev/mcp

Tools

Tool	Description
search_caniuse	Search Can I Use features by keyword. Returns feature names, descriptions, and global support percentages.
get_caniuse_support	Get detailed browser support for a specific feature — per-browser version support, usage percentages, spec links, notes, and resources.

Data Sources

Data	Source	Cache TTL
Feature data	Fyrd/caniuse (GitHub raw JSON)	6 hours

---

Node.js API MCP

Search and read Node.js API documentation — modules, classes, methods, events, with stability indicators and version history.

Endpoint: https://nodejs-mcp.jasnell.workers.dev/mcp

Tools

Tool	Description
list_nodejs_modules	List all ~50 Node.js API modules with stability indicators. Optionally filter by name.
get_nodejs_module	Fetch the overview and member listing for a module — stability level, classes, methods, events.
search_nodejs_module	Search within a specific module for methods, classes, or events by name.
get_nodejs_section	Fetch a specific section from a module's documentation as markdown.

Data Sources

Data	Source	Cache TTL
Module documentation	nodejs/node doc/api/ (GitHub raw Markdown)	6 hours

---

TypeScript MCP

Search the TypeScript Handbook, look up tsconfig compiler options, and read release notes.

Endpoint: https://typescript-mcp.jasnell.workers.dev/mcp

Tools

Tool	Description
search_typescript_handbook	Search TypeScript handbook pages by topic (narrowing, generics, mapped types, etc.).
get_typescript_handbook_page	Fetch a specific handbook page as markdown.
get_tsconfig_option	Get documentation for a specific TypeScript compiler option (strictNullChecks, module, target, etc.).
list_tsconfig_options	List all compiler options, optionally filtered by category (type-checking, modules, emit, etc.).
get_typescript_release_notes	Fetch release notes for a specific TypeScript version.

Data Sources

Data	Source	Cache TTL
Handbook content	microsoft/TypeScript-Website (GitHub raw Markdown)	6 hours
TSConfig option docs	microsoft/TypeScript-Website tsconfig-reference/	6 hours
Release notes	microsoft/TypeScript-Website documentation/	24 hours

Project Structure

packages/
├── shared/                   @mcp/shared — shared utilities
│   └── src/
│       ├── cache.ts          Cloudflare Cache API + in-memory fallback
│       ├── html-to-markdown.ts   HTML → simplified markdown converter
│       └── search.ts         Scored search utility
├── whatwg-spec-mcp/          WHATWG MCP Worker
│   └── src/
│       ├── index.ts          Worker entry point
│       ├── lib/              Data fetching and parsing
│       └── tools/            One file per MCP tool
├── ietf-spec-mcp/           IETF MCP Worker
│   └── src/
│       ├── index.ts          Worker entry point
│       ├── lib/              Datatracker client, RFC/draft parsers
│       └── tools/            One file per MCP tool
├── mdn-mcp/                 MDN MCP Worker
│   └── src/
│       ├── index.ts          Worker entry point
│       ├── lib/              MDN search, content, compat data clients
│       └── tools/            One file per MCP tool
├── wpt-mcp/                 WPT MCP Worker
│   └── src/
│       ├── index.ts          Worker entry point
│       ├── lib/              wpt.fyi client, test file/directory access
│       └── tools/            One file per MCP tool
├── w3c-spec-mcp/            W3C Specs MCP Worker
│   └── src/
│       ├── index.ts          Worker entry point
│       ├── lib/              W3C API client, CSS spec parser
│       └── tools/            One file per MCP tool
├── caniuse-mcp/             Can I Use MCP Worker
│   └── src/
│       ├── index.ts          Worker entry point
│       ├── lib/              Caniuse data client
│       └── tools/            One file per MCP tool
├── nodejs-mcp/              Node.js API MCP Worker
│   └── src/
│       ├── index.ts          Worker entry point
│       ├── lib/              Node.js docs parser
│       └── tools/            One file per MCP tool
└── typescript-mcp/          TypeScript MCP Worker
    └── src/
        ├── index.ts          Worker entry point
        ├── lib/              Handbook, tsconfig, release notes clients
        └── tools/            One file per MCP tool

This is an npm workspaces monorepo. The @mcp/shared package provides caching, HTML-to-markdown conversion, and search utilities consumed by all eight workers.

Development

npm install

# Start WHATWG MCP locally (http://localhost:8787/mcp)
npm start -w packages/whatwg-spec-mcp

# Start IETF MCP locally (http://localhost:8787/mcp)
npm start -w packages/ietf-spec-mcp

# Start MDN MCP locally (http://localhost:8787/mcp)
npm start -w packages/mdn-mcp

# Start WPT MCP locally (http://localhost:8787/mcp)
npm start -w packages/wpt-mcp

# Start W3C MCP locally (http://localhost:8787/mcp)
npm start -w packages/w3c-spec-mcp

# Start Can I Use MCP locally (http://localhost:8787/mcp)
npm start -w packages/caniuse-mcp

# Start Node.js MCP locally (http://localhost:8787/mcp)
npm start -w packages/nodejs-mcp

# Start TypeScript MCP locally (http://localhost:8787/mcp)
npm start -w packages/typescript-mcp

Deploy

# Deploy all
npm run deploy -w packages/whatwg-spec-mcp
npm run deploy -w packages/ietf-spec-mcp
npm run deploy -w packages/mdn-mcp
npm run deploy -w packages/wpt-mcp
npm run deploy -w packages/w3c-spec-mcp
npm run deploy -w packages/caniuse-mcp
npm run deploy -w packages/nodejs-mcp
npm run deploy -w packages/typescript-mcp

Architecture

• Stateless — Per-request McpServer instances, no Durable Objects.
• No authentication — All data sources are public.
• Caching — Cloudflare Cache API in production, in-memory Map fallback for local dev.
• HTML-to-markdown — Regex-based extraction converts spec HTML to simplified markdown suitable for LLM consumption.