Applied Form Standards MCP server

Standards by Applied Form

A design-system conformance gate measured in a real browser. Give it a DTCG token file and a page; it renders the page in Chromium at four fixed widths and two sampled ones, under reduced motion and in print, and checks every computed value against the system's rules. It reports what the browser drew, not what the stylesheet says.

Standards is open so the evidence about it can be checked. Every comparison it is quoted in can be rerun from this repository: the gate beside axe-core and stylelint, the drift survey of public design systems, and the model study and its judging rounds, with every record they were scored from.

Start

npm install @appliedform/standards && npx playwright install chromium
npx standards init --pack instrument  # load a system: the free Standards pack, or your pack's tokens.json
npx standards lint page.html          # your page, judged by that system's rules, at every width

With no system loaded, standards lint judges a page by the rules that hold for any page (contrast, focus, target size, overflow, alt text, heading order, motion) and says how to load one. For an agent, npx standards mcp-config prints the server block for Claude Code or Cursor.

Use

npx standards lint page.html https://example.com/page      # every rule, every width
npx standards lint https://example.com/ --register ii      # a page that has not declared a register
npx standards baseline https://example.com/a --out standards-baseline.json
npx standards lint https://example.com/a --baseline standards-baseline.json
npx standards fix page.html                                # apply the fixes it can make; writes page.fixed.html
npx standards audit pages/ --fix                           # every page in a folder, as found and as the fixer would leave it, as one report
npx standards drift https://example.com/ --out drift.json  # what system a site actually renders
npx standards rules                                        # every rule, its severity and what it checks
npx standards mcp                                          # the same tools for a model, over MCP

standards fix exits 0 when the fixed page passes every checked rule, 1 when violations remain, and lists what it could not fix by rule and element. standards audit writes one self-contained HTML page (and --json) with the findings by rule and by page, the WCAG criteria the rules touch, what is not checked, and the command that repeats the run. standards lint exits 1 on any error-severity violation not held in the baseline. standards.config.json sets a rule to error, warn or off; standards.config.example.json is a starting point. The exception is a mandatory rule: contrast, text-too-small, target-size, focus-hidden, link-not-underlined, alt-missing, horizontal-overflow and wordmark-live-text, listed under $extensions["form.applied"].levels.mandatory in the token file. A config that sets one of them to warn or off is refused, and standards lint exits 2 (decision 0027 in the Applied Form repository). A system loaded over the token file may raise the thresholds contrast and text-too-small read (floors.body-contrast, display-contrast, large-text-px, large-bold-text-px, text-min-px) and is refused if it lowers one below the token file's own value. A system that declares a pack and states no register.pack is refused too: it judged every page by register alone and then dropped that house rule, so no mandatory rule was measured. So is a system with a register whose background is not a colour. Four gaps are known. On a page whose register the loaded system does not define, with or without a system, a config that lowers register leaves the mandatory rules unmeasured. A system file that declares itself a pack is judged without text-too-small, link-not-underlined and wordmark-live-text. On a page that paints no ground, contrast measures against the ground the system names. The MCP tools standards_lint and standards_fix measure only the widths a caller names, so a call without 320 never measures horizontal-overflow at 320px.

Names that changed

Standards 5.0.0 removed the names the product had before it was called Standards: the af and af-mcp commands, the af_* MCP tools, AF_BRAND and AF_CHROMIUM, af.config.json, af-baseline.json and .af/. They are not read: standards stops with exit status 2 and one line naming the replacement when a variable or file under an old name is in use. standards, the standards_* tools, STANDARDS_SYSTEM, STANDARDS_CHROMIUM, standards.config.json, standards-baseline.json and .standards/ replace them, and the default report file is standards-audit.html. Uninstall @appliedform/engine before installing @appliedform/standards: both ship the af and af-mcp bins, so a global install of one over the other fails with EEXIST. The full list, with what to change, is in docs/migrating-to-5.md.

Documents recorded before the rename, such as the decision records and the evaluation protocol and its results, use the old names, and are not rewritten.

The token file

tokens/applied-form.tokens.json is the Reference system: Standards' structure (registers, voices, spacing, floors and every rule's parameters) with a neutral palette derived by standards brand. It exists so Standards can be tested and published. It is not a design to ship. Point it at your own system by replacing the file, or by importing a Standards pack with standards system import.

Evidence

The protocol was written before the runs it governs, and it says what result would count against Standards. These run from a clone of this repository: the npm package carries Standards and nothing that needs a model SDK, axe-core or stylelint.

Develop

npm install
npm run check    # build, unit tests, and the clean fixture linted in a real browser

Tests use node:test. Set STANDARDS_CHROMIUM to a Chromium executable if Playwright has not downloaded one.

Licence

Apache-2.0. See LICENSE and NOTICE. The name Applied Form and its marks are not licensed.