Designers

Motion check

check_motion

Read-only

Static motion audit against WCAG 2.2 (2.2.2 Pause, Stop, Hide; 2.3.1 Three Flashes; 2.3.3 Animation from Interactions). Pass html and/or css, or a public url (the page and up to 4 same-site stylesheets are fetched). Flags autoplay video and audio, marquee and blink, infinite animations with no pause control, animation patterns that could flash (it cannot measure flash rate), parallax and scroll-linked motion, large translate or scale transitions, smooth scrolling, and durations over 400ms. Reports whether prefers-reduced-motion is honored (counts animations and transitions against reduced-motion rules) and returns a ready-to-paste reduced-motion CSS block. Each finding names its criterion, severity and fix. Reads source only; does not render the page or run script.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "check_motion"
  }
}

Input Schema

Name	Required	Description
`css`	No	CSS text to analyze, with or without html.
`url`	No	A public page to fetch instead. Up to 4 same-site stylesheets are fetched too.
`html`	No	Page HTML source. Optional if url is given.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 28, 2026

changedInput schema / properties / css / description

Previous value: -"CSS text to analyse, with or without html."New value: +"CSS text to analyze, with or without html."

AddedOct 23, 2026

TDQS

A4.1/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations only declare read-only and open-world; the description adds substantial context beyond them: the URL mode performs network fetching of the page plus up to 4 same-site stylesheets, the tool explicitly cannot measure flash rate, it does not render or run script, and it returns a ready-to-paste reduced-motion CSS block alongside findings with criterion, severity and fix. These are exactly the operational limits an agent needs before calling.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the purpose and criteria, then inputs, then detection scope, then output. It is long for a single paragraph, but nearly every clause carries actionable detail (flash-rate limitation, stylesheet fetch cap, reduced-motion output) rather than filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

No output schema exists, so the description carries the burden of describing returns — it does so concretely (per-finding criterion/severity/fix, reduced-motion CSS block, reduced-motion honoring counts). Combined with the disclosed source-only analysis constraint, an agent has everything needed to call it correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so all three parameters are already documented, and the description mostly restates the html/css/url combination rule. It does not say what happens when no parameters are supplied (none are required), which is the one genuinely ambiguous case left to the agent.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource — a static motion audit scoped to WCAG 2.2.2, 2.3.1 and 2.3.3 — and enumerates the exact patterns it flags (autoplay media, marquee/blink, infinite animations, parallax, durations over 400ms). That enumeration separates it from nearby siblings such as audit_motion_css or review_animation_principles, but no sibling is named explicitly.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Clear invocation guidance: supply `html` and/or `css`, or a public `url` instead. It also states the operational boundary — source-only analysis, no rendering or scripting — which tells the agent when this tool is the wrong choice for a live rendered page. It stops short of naming which sibling to use for rendered or interaction-based motion review.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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