How do I install Atag?

Copy the stdio config for Cursor, Claude Desktop, Claude Code, or VS Code on this page. It uses the publisher's install, not a PlugMCP proxy.

Does Atag need an API key?

No required environment variable is listed on this record.

When was Atag last checked?

Last checked 2026-11-09. ATAG 2.0 (Authoring Tool Accessibility Guidelines) guidance for authoring tool developers

Atag MCP server

Power your agent

Add this server

The publisher's own command. Not a PlugMCP endpoint.

Add to Cursor Add to VS Code Run on PlugMCP

Host a copy with our keys and logs.

Local command

npx -y [email protected]

Claude Code has no install link for a local command. Copy the command below and run it in a terminal.

shClaude Code

1claude mcp add io.github.mmasey-atag-mcp -- npx -y atag-mcp@1.0.2

Run in a terminal.

jsonClaude Desktop

1{2  "mcpServers": {3    "io.github.mmasey-atag-mcp": {4      "command": "npx",5      "args": [6        "-y",7        "[email protected]"8      ]9    }10  }11}

claude_desktop_config.json

Local · npmPublisher installStep-by-step: add this in Claude

Remote URL or a command on your machine? How the two installs differ

Run on PlugMCP

Host a copy with our keys and logs.

A new server you create. It is not this listing's official endpoint. Use the publisher install when you want their URL and their credentials.

Launch

Server facts

Local

Transport: stdio
Version: 1.0.2
Last checked

Tools

No tool list yet. Remote servers get one after the first health check.

FAQ

Questions

ATAG MCP

An MCP (Model Context Protocol) server that provides guidance on ATAG 2.0 — the W3C Authoring Tool Accessibility Guidelines — to help authoring tool developers build more accessible software.

What is ATAG?

ATAG 2.0 defines how authoring tools (rich-text editors, CMSes, IDEs, website builders, etc.) should:

Part A — Be accessible to authors with disabilities (the tool's own UI)
Part B — Help authors produce accessible web content (alt text prompts, accessibility checkers, accessible templates, etc.)

Why this exists

ATAG 2.0 has been a W3C Recommendation since 2015, but adoption among authoring tools remains limited — partly because the guidance is easy to overlook at the moment design and implementation decisions are actually made. With more authoring tool features now being built with the help of AI coding assistants, this server puts the full spec within the assistant's reach: describe the feature you're working on (an image upload dialog, a rich-text toolbar, a template picker) and get back the actual success criteria that apply, rather than a half-remembered summary. The aim is to lower the cost of considering ATAG at all — the first step towards tools that support it.

The data is a static, hand-checked copy of the ATAG 2.0 spec — not fetched or generated at runtime — so answers stay faithful to the W3C source. A weekly workflow checks for upstream spec changes.

Tools

Tool	Description
`get-server-info`	Dataset statistics and attribution
`explain-atag`	Overview of ATAG, how it differs from WCAG, and its two-part structure
`list-parts`	Part A and Part B summaries
`list-principles`	All 8 principles, filterable by part
`list-guidelines`	All 24 guidelines, filterable by part or principle
`list-success-criteria`	All 63 success criteria, filterable by part, principle, guideline, or level
`get-criterion`	Full details for a specific SC (e.g. `B.2.3.1`)
`get-guideline`	Full guideline details with all child success criteria
`get-criteria-by-level`	All criteria at Level A, AA, or AAA
`search-atag`	Keyword search across all ATAG content
`list-glossary-terms`	All ATAG glossary terms
`get-glossary-term`	Definition of a specific ATAG term
`get-guidance`	Key tool — describe a feature you're building and get the most relevant ATAG criteria

Setup

No local install required — add the config below and your MCP client will fetch the package automatically via npx.

Claude Desktop

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

{
  "mcpServers": {
    "atag-mcp": {
      "command": "npx",
      "args": ["-y", "atag-mcp"]
    }
  }
}

VS Code (Claude extension)

{
  "mcp": {
    "servers": {
      "atag-mcp": {
        "type": "stdio",
        "command": "npx",
        "args": ["-y", "atag-mcp"]
      }
    }
  }
}

Local development install

npm install
npm run build
# then point your config to dist/index.js directly

Usage examples

Ask Claude:

"What ATAG criteria apply to an image insertion dialog?" → uses get-guidance
"Show me all Level A criteria from Part B" → uses get-criteria-by-level
"Explain guideline B.3.1" → uses get-guideline
"What does 'editing-view' mean in ATAG?" → uses get-glossary-term
"Search ATAG for keyboard access" → uses search-atag

Development

npm run dev          # Run server directly with tsx (no compile step)
npm test             # Run all tests
npm run test:watch   # Watch mode
npm run validate-data  # Validate data/atag.json structure
npm run check-updates  # Check if W3C spec has changed

Branching and commits

This project follows git flow with Conventional Commits:

main — released code only; every merge to main is tagged and published
develop — integration branch; day-to-day work lands here
feature/<name> — branched from and merged back to develop
release/<version> — branched from develop, merged to main (tagged) and back to develop
hotfix/<name> — branched from main for urgent fixes, merged to both main and develop

Commit messages use conventional prefixes: feat:, fix:, docs:, test:, ci:, chore:, refactor: (with ! or a BREAKING CHANGE: footer for breaking changes).

Releasing

Versioning uses standard npm version bumps. Pushing a v* tag triggers the GitHub Actions publish workflow, which runs tests and publishes to npm automatically.

npm version patch   # bug fixes:    1.0.0 → 1.0.1
npm version minor   # new features: 1.0.0 → 1.1.0
npm version major   # breaking:     1.0.0 → 2.0.0

git push && git push --tags

When bumping the version, also update the version fields in server.json to match — the MCP Registry validates them against the published npm package. After the npm publish succeeds, refresh the registry listing with:

mcp-publisher login github
mcp-publisher publish

Publishing requires the NPM_TOKEN repository secret (a granular npm access token with write access to atag-mcp). If the token expires or is rotated, add the new one under the same secret name, then run the manual Check npm token workflow (Actions tab) to verify it authenticates before tagging a release.

Keeping data current

The ATAG 2.0 spec is captured in data/atag.json. The GitHub Actions workflow (.github/workflows/update-atag.yml) runs weekly and opens an issue if the W3C spec content changes.

To update manually:

Review changes at https://www.w3.org/TR/ATAG20/
Edit data/atag.json with the changes
Run npm run validate-data to check structure
Run npm run check-updates -- --save to update the stored hash

Data

Version: ATAG 2.0
Specification: https://www.w3.org/TR/ATAG20/
Parts: 2 (Part A + Part B)
Principles: 8
Guidelines: 24
Success Criteria: 63
Glossary Terms: 18

License

MIT

Atag

Add this server

Host a copy with our keys and logs.

Server facts

Tools

Questions

How do I install Atag?

Does Atag need an API key?

What transport does Atag use?

When was Atag last checked?

Documentation

ATAG MCP

What is ATAG?

Why this exists

Tools

Setup

Claude Desktop

VS Code (Claude extension)

Local development install

Usage examples

Development

Branching and commits

Releasing

Keeping data current

Data

License