new_audit(ard-schema): add Agent Resource Discovery gatherer and schema audit

core/audits/agentic/ard-schema.js

@@ -0,0 +1,160 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * @fileoverview Audit that validates ai-catalog.json manifests against the Agentic Resource Discovery (ARD) specification.
+ *
+ * This implementation is a direct JavaScript port of `validate_manifest` from the official ARD Conformance Test suite:
+ * @see https://github.com/ards-project/ard-spec/blob/main/conformance/bin/conformance-test
+ * @see https://agenticresourcediscovery.org/spec/
+ * @version ARD Spec 1.0 / ADR-0003
+ */
+
+import {Audit} from '../audit.js';
+import * as i18n from '../../lib/i18n/i18n.js';
+import {ConformanceTester} from '../../../third-party/ard/ard.js';
+
+const UIStrings = {
+  /** Title of a Lighthouse audit that evaluates whether ai-catalog.json conforms to the ARD specification. Shown when valid. */
+  title: '`ai-catalog.json` schema is valid',
+  /** Title of a Lighthouse audit that evaluates whether ai-catalog.json conforms to the ARD specification. Shown when invalid. */
+  failureTitle: '`ai-catalog.json` schema is invalid or has warnings',
+  /** Description of a Lighthouse audit that tells the user why ai-catalog.json must match the ARD specification. */
+  description: 'Valid `ai-catalog.json` manifests are required for autonomous ' +
+    'AI agents and registries to discover and verify your resources. ' +
+    '[Learn more about the ARD specification](https://agenticresourcediscovery.org/spec/).',
+  /** Explanatory message stating that ai-catalog.json could not be loaded for schema validation. */
+  explanation: 'Catalog file could not be loaded for schema validation.',
+  /** Warning message explaining that representativeQueries are missing for an entry. */
+  missingRepresentativeQueries: 'Missing `representativeQueries`. Providing examples ' +
+    'significantly improves discoverability.',
+  /** Header of the table column which displays the issue. */
+  columnIssue: 'Issue',
+  /** Header of the table column which displays the severity. */
+  columnSeverity: 'Severity',
+  /** Table item value for an error severity. */
+  itemSeverityError: 'Error',
+  /** Table item value for a warning severity. */
+  itemSeverityWarning: 'Warning',
+};
+
+const str_ = i18n.createIcuMessageFn(import.meta.url, UIStrings);
+
+class ArdSchema extends Audit {
+  /**
+   * @return {LH.Audit.Meta}
+   */
+  static get meta() {
+    return {
+      id: 'ard-schema',
+      title: str_(UIStrings.title),
+      failureTitle: str_(UIStrings.failureTitle),
+      description: str_(UIStrings.description),
+      requiredArtifacts: ['AgentResourceDiscovery'],
+      supportedModes: ['navigation', 'snapshot'],
+    };
+  }
+
+  /**
+   * @param {LH.Artifacts} artifacts
+   * @return {LH.Audit.Product}
+   */
+  static audit(artifacts) {
+    const ard = artifacts.AgentResourceDiscovery;
+    const signals = ard.discoverySignals;
+
+    const hasExplicitSignal = Boolean(
+      signals.robotsTxtAgentmap ||
+      signals.htmlLink ||
+      signals.httpHeaderLink
+    );
+    const hasCatalog = hasExplicitSignal || ard.status === 200;
+
+    if (!hasCatalog) {
+      return {
+        score: 1,
+        notApplicable: true,
+      };
+    }
+
+    if (ard.status !== 200 || !ard.content) {
+      return {
+        score: 0,
+        explanation: str_(UIStrings.explanation),
+      };
+    }
+
+    const itemSeverityError = str_(UIStrings.itemSeverityError);
+    const itemSeverityWarning = str_(UIStrings.itemSeverityWarning);
+
+    /** @type {Array<{element: string, issue: string | LH.IcuMessage, severity: LH.IcuMessage}>} */
+    const issues = [];
+
+    /** @type {LH.Audit.Details.Table['headings']} */
+    const headings = [
+      {key: 'element', valueType: 'text', label: str_(i18n.UIStrings.columnElement)},
+      {key: 'issue', valueType: 'text', label: str_(UIStrings.columnIssue)},
+      {key: 'severity', valueType: 'text', label: str_(UIStrings.columnSeverity)},
+    ];
+
+    const tester = new ConformanceTester();
+    tester.validate_manifest(ard.content, 'ai-catalog.json');
+
+    for (const err of tester.errors) {
+      issues.push({
+        element: err.element,
+        issue: err.message,
+        severity: itemSeverityError,
+      });
+    }
+
+    for (const warn of tester.warnings) {
+      issues.push({
+        element: warn.element,
+        issue: warn.message,
+        severity: itemSeverityWarning,
+      });
+    }
+
+    // Lighthouse Best Practice: Recommend representativeQueries for better discoverability
+    try {
+      const manifest = JSON.parse(ard.content);
+      if (manifest && Array.isArray(manifest.entries)) {
+        for (let i = 0; i < manifest.entries.length; i++) {
+          const entry = manifest.entries[i];
+          if (!entry.representativeQueries || entry.representativeQueries.length === 0) {
+            const label = entry.displayName || entry.identifier || `Entry #${i}`;
+            issues.push({
+              element: label,
+              issue: str_(UIStrings.missingRepresentativeQueries),
+              severity: itemSeverityWarning,
+            });
+          }
+        }
+      }
+    } catch (e) {
+      // Ignore parse errors as ConformanceTester catches them
+    }
+
+    const hasErrors = issues.some(i => i.severity === itemSeverityError);
+    const hasWarnings = issues.some(i => i.severity === itemSeverityWarning);
+
+    let score = 1;
+    if (hasErrors) {
+      score = 0;
+    } else if (hasWarnings) {
+      score = 0.5;
+    }
+
+    return {
+      score,
+      details: issues.length ? Audit.makeTableDetails(headings, issues) : undefined,
+    };
+  }
+}
+
+export default ArdSchema;
+export {UIStrings};

core/config/agentic-browsing-config.js

@@ -23,6 +23,11 @@ const UIStrings = {
   /** Description of the Agent Accessibility group of audits. */
   agentAccessibilityGroupDescription: 'These audits highlight best practices for improving the ' +
   'accessibility of the website for AI agents.',
+  /** Title of the Agentic Resource Discovery (ARD, https://agenticresourcediscovery.org/spec/) group of audits. */
+  ardGroupTitle: 'Agentic Resource Discovery',
+  /** Description of the Agentic Resource Discovery (ARD, https://agenticresourcediscovery.org/spec/) group of audits. */
+  ardGroupDescription: 'These audits validate that agentic resources are ' +
+    'discoverable, reachable, and conform to the ARD specification.',
 };
 
 const str_ = i18n.createIcuMessageFn(import.meta.url, UIStrings);
@@ -36,11 +41,13 @@ const config = {
     'webmcp-form-coverage',
     'webmcp-schema-validity',
     'agentic/llms-txt',
+    'agentic/ard-schema',
   ],
   artifacts: [
     {id: 'WebMCP', gatherer: 'webmcp'},
     {id: 'WebMcpSchemaIssues', gatherer: 'webmcp-schema'},
     {id: 'LlmsTxt', gatherer: 'agentic/llms-txt'},
+    {id: 'AgentResourceDiscovery', gatherer: 'agentic/ard'},
   ],
   groups: {
     'webmcp': {
@@ -51,6 +58,10 @@ const config = {
       title: str_(UIStrings.agentAccessibilityGroupTitle),
       description: str_(UIStrings.agentAccessibilityGroupDescription),
     },
+    'agent-resource-discovery': {
+      title: str_(UIStrings.ardGroupTitle),
+      description: str_(UIStrings.ardGroupDescription),
+    },
   },
   categories: {
     'agentic-browsing': {
@@ -65,6 +76,7 @@ const config = {
         {id: 'webmcp-schema-validity', weight: 1, group: 'webmcp'},
         {id: 'cumulative-layout-shift', weight: 1, acronym: 'CLS'},
         {id: 'llms-txt', weight: 1, group: 'agent-accessibility'},
+        {id: 'ard-schema', weight: 1, group: 'agent-resource-discovery'},
       ],
     },
   },

core/config/default-config.js

@@ -115,6 +115,11 @@ const UIStrings = {
   /** Description of the Agent Accessibility group of audits. */
   agentAccessibilityGroupDescription: 'These audits highlight best practices for improving the ' +
   'accessibility of the website for AI agents.',
+  /** Title of the Agentic Resource Discovery (ARD, https://agenticresourcediscovery.org/spec/) group of audits. */
+  ardGroupTitle: 'Agentic Resource Discovery',
+  /** Description of the Agentic Resource Discovery (ARD, https://agenticresourcediscovery.org/spec/) group of audits. */
+  ardGroupDescription: 'These audits validate that agentic resources are ' +
+    'discoverable, reachable, and conform to the ARD specification.',
 };
 
 const str_ = i18n.createIcuMessageFn(import.meta.url, UIStrings);
@@ -145,6 +150,7 @@ const defaultConfig = {
     {id: 'MetaElements', gatherer: 'meta-elements'},
     {id: 'NetworkUserAgent', gatherer: 'network-user-agent'},
     {id: 'RobotsTxt', gatherer: 'seo/robots-txt'},
+    {id: 'AgentResourceDiscovery', gatherer: 'agentic/ard'},
     {id: 'Scripts', gatherer: 'scripts'},
     {id: 'SourceMaps', gatherer: 'source-maps'},
     {id: 'Stacks', gatherer: 'stacks'},
@@ -302,6 +308,7 @@ const defaultConfig = {
     'webmcp-form-coverage',
     'webmcp-schema-validity',
     'agentic/llms-txt',
+    'agentic/ard-schema',
     'bf-cache',
     'insights/cache-insight',
     'insights/cls-culprits-insight',
@@ -397,6 +404,10 @@ const defaultConfig = {
       title: str_(UIStrings.agentAccessibilityGroupTitle),
       description: str_(UIStrings.agentAccessibilityGroupDescription),
     },
+    'agent-resource-discovery': {
+      title: str_(UIStrings.ardGroupTitle),
+      description: str_(UIStrings.ardGroupDescription),
+    },
     // Group for audits that should not be displayed.
     'hidden': {title: ''},
   },
@@ -644,6 +655,7 @@ const defaultConfig = {
         {id: 'webmcp-schema-validity', weight: 1, group: 'webmcp'},
         {id: 'cumulative-layout-shift', weight: 1, acronym: 'CLS'},
         {id: 'llms-txt', weight: 1, group: 'agent-accessibility'},
+        {id: 'ard-schema', weight: 1, group: 'agent-resource-discovery'},
       ],
     },
   },

core/gather/fetcher.js

@@ -10,7 +10,7 @@ import * as LH from '../../types/lh.js';
  * ignoring normal browser constraints such as CORS.
  */
 
-/** @typedef {{content: string|null, status: number|null}} FetchResponse */
+/** @typedef {{content: string|null, status: number|null, headers?: Record<string, string>|null}} FetchResponse */
 
 class Fetcher {
   /**
@@ -37,6 +37,26 @@ class Fetcher {
     return this._fetchResourceOverProtocol(url, options);
   }
 
+  /**
+   * @param {Headers|Record<string, string|number|boolean>|null|undefined} rawHeaders
+   * @return {Record<string, string>|null}
+   */
+  _normalizeHeaders(rawHeaders) {
+    if (!rawHeaders) return null;
+
+    /** @type {Record<string, string>} */
+    const headers = {};
+    const entries = typeof /** @type {Headers} */ (rawHeaders).entries === 'function' ?
+    /** @type {Headers} */ (rawHeaders).entries() :
+      Object.entries(rawHeaders);
+
+    for (const [key, value] of entries) {
+      headers[key.toLowerCase()] = String(value);
+    }
+
+    return headers;
+  }
+
   /**
    * @param {string} url
    * @return {Promise<FetchResponse>}
@@ -49,9 +69,12 @@ class Fetcher {
       content = await response.text();
     } catch {}
 
+    const headers = this._normalizeHeaders(response.headers);
+
     return {
       content,
       status: response.status,
+      headers,
     };
   }
 
@@ -82,7 +105,7 @@ class Fetcher {
 
   /**
    * @param {string} url
-   * @return {Promise<{stream: LH.Crdp.IO.StreamHandle|null, status: number|null}>}
+   * @return {Promise<{stream: LH.Crdp.IO.StreamHandle|null, status: number|null, headers?: Record<string, string>|null}>}
    */
   async _loadNetworkResource(url) {
     const frameTreeResponse = await this.session.sendCommand('Page.getFrameTree');
@@ -98,6 +121,7 @@ class Fetcher {
     return {
       stream: networkResponse.resource.success ? (networkResponse.resource.stream || null) : null,
       status: networkResponse.resource.httpStatusCode || null,
+      headers: networkResponse.resource.headers || null,
     };
   }
 
@@ -110,12 +134,14 @@ class Fetcher {
     const startTime = Date.now();
     const response = await this._wrapWithTimeout(this._loadNetworkResource(url), options.timeout);
 
+    const headers = this._normalizeHeaders(response.headers);
+
     const isOk = response.status && response.status >= 200 && response.status <= 299;
-    if (!response.stream || !isOk) return {status: response.status, content: null};
+    if (!response.stream || !isOk) return {status: response.status, content: null, headers};
 
     const timeout = options.timeout - (Date.now() - startTime);
     const content = await this._readIOStream(response.stream, {timeout});
-    return {status: response.status, content};
+    return {status: response.status, content, headers};
   }
 
   /**