audit_url
Run accessibility checks against a live URL. Catches dynamic behaviour (focus management, transitions, live regions) that audit_html cannot. NOTE: it drives a fresh headless browser with no app state — for routes that depend on localStorage / auth / prior interaction, seed localStorage (or initSc...
This record as markdown: /tools/a11y-assist-mcp/audit-url.md
What audit_url does on A11y Assist
AI agents invoke audit_url to trigger actions in A11y Assist. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call: builds kicked off, notifications sent, workflows started.
| Parameter | Type | Required | Description |
|---|---|---|---|
url | string | Yes | URL to audit. Storybook story, dev server route, staging page, anywhere reachable from this machine. |
initScript | string | — | JavaScript to run before the page's own scripts (Playwright addInitScript) — e.g. to seed cookies or app state. Trusted/dev use only. |
localStorage | object | — | Seed localStorage entries (key→value) BEFORE the page loads, so state-dependent routes render real content. audit_url otherwise starts from a fresh browser with |
waitForSelector | string | — | CSS selector to wait for before running axe — useful for SPAs or async content. |
Parameters from the server's own tool schema.
Why audit_url is rated High
audit_url triggers real processes with real consequences. An agent gone sideways doesn't fire it once. It starts dozens of builds, sends mass notifications, or burns through compute before anyone looks up.
Risk signalsAccepts URL/endpoint input (url)
Attacks that exploit this kind of access
The rule that runs audit_url safely
PolicyLayer is an MCP gateway: it sits between your AI agents and A11y Assist, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For audit_url, this is the rule to start with:
audit_url stays usable, but rate-capped: a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect A11y Assist, apply this rule, and every audit_url call is checked against it from then on.
Questions about audit_url
Run accessibility checks against a live URL. Catches dynamic behaviour (focus management, transitions, live regions) that audit_html cannot. NOTE: it drives a fresh headless browser with no app state — for routes that depend on localStorage / auth / prior interaction, seed localStorage (or initScript) so the real view renders, and check the returned audited block to confirm which view was tested. It is categorised as a Execute tool in the A11y Assist MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
audit_url accepts 4 parameters: url, initScript, localStorage, waitForSelector. Required: url. The full parameter table on this page comes from the server's own tool schema.
Register the A11y Assist MCP server in PolicyLayer and add a rule for audit_url: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches A11y Assist. Nothing to install.
audit_url is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the audit_url rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for audit_url. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
audit_url is provided by the A11y Assist MCP server (a11y-assist-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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