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Lighthouse Agentic Browsing: what it checks

The seven audits in Lighthouse's Agentic Browsing category, what each one needs to pass, and how to fix the accessibility tree, WebMCP and llms.txt findings.

Lighthouse, the audit tool built into Chrome DevTools and PageSpeed Insights, has a category for AI agents: Agentic Browsing. It arrived in Lighthouse 13.3.0 in May 2026 and asks a narrower question than an AI search audit: can an agent that drives a browser understand and operate this page?

Google labels it experimental: “This category is still under development and subject to change.”

How it scores

Unlike Performance or SEO, the category has no 0–100 score. It shows a fraction, the number of audits that pass out of those that apply, so a page can show 4/5 rather than 80.

Testing it in DevTools needs Chrome 150 or later. The WebMCP audits need the WebMCP origin trial. Lighthouse 13.4.1 enabled the category in the PageSpeed Insights API.

The seven audits

These are the audits in the category in the current Lighthouse configuration.

Accessibility tree is well-formed

agent-accessibility-tree. Agents read the accessibility tree, the same structure screen readers use. Chrome’s documentation calls it their “primary data model”. This audit runs a subset of the accessibility audits in three groups: names and labels, tree integrity, and visibility.

To pass: give every button, link and form field an accessible name, use real <button>, <a> and <label> elements instead of clickable <div>s, keep ARIA roles valid, and do not hide interactive content from the tree.

WebMCP tools registered

webmcp-registered-tools. Lists the WebMCP tools the page registered when Lighthouse analysed it, both declarative (forms) and imperative (JavaScript), with their names, descriptions and input schemas. Lighthouse warns when a page registers more tools than it recommends, because each tool “consumes model context tokens, adds latency, and increases the risk of tool confusion.”

WebMCP form coverage

webmcp-form-coverage. Lists forms without WebMCP annotations and suggests adding them. It passes when every form is covered.

WebMCP schemas are valid

webmcp-schema-validity. Reports the schema errors the browser found: a form without toolname or tooldescription, a field without a name, a field without a description. WebMCP and the attributes are covered in WebMCP: let AI agents use your forms.

Cumulative Layout Shift

cumulative-layout-shift, the same metric as in Performance. An agent locates an element and then clicks where it was; if the layout moves in between, it clicks the wrong thing. Reserve space for images, embeds and banners.

llms.txt follows recommendations

llms-txt. Fetches /llms.txt. A missing file is not applicable, because the file is optional. A server error fails the audit, and so does a file without an H1 heading, a file that is suspiciously short, or one without links. See llms.txt: what it is.

ARD manifest is valid

ard-schema, added in Lighthouse 13.5.0. Agentic Resource Discovery is a proposed manifest at /.well-known/ard.json, or linked with rel="ard", that lists the resources an agent can use: MCP servers, agents, API descriptions. Lighthouse 13.6.0 follows ARD 0.91, which replaced the older /.well-known/ai-catalog.json. A site with nothing for agents to call does not need one.

What it does not check

The category is about operating a page in a browser. It does not look at whether AI crawlers may fetch the page, whether the content is in the HTML without JavaScript, or whether a firewall blocks AI bots, which decide whether the page reaches AI search at all. Those are covered in Is your site agent-ready?.

Run it

In Chrome 150 or later, open DevTools, go to the Lighthouse panel, tick Agentic Browsing and analyse the page. From the command line:

npx lighthouse https://example.com --only-categories=agentic-browsing --view

A CrawlWise scan runs axe accessibility checks, measures layout shift, reads llms.txt, records the WebMCP tools a page registers and validates an ARD manifest, alongside the crawler access and content checks Lighthouse leaves out.

Sources

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