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Lighthouse MCP

by danielsogl
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Compare Mobile vs Desktop

compare_mobile_desktop
Read-only

Compare mobile and desktop performance metrics using Lighthouse audits to identify optimization opportunities and improve user experience.

Instructions

Compare website performance between mobile and desktop devices

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
urlYesURL to audit
categoriesNo
throttlingNoWhether to throttle the audit (default: false)
includeDetailsNoInclude detailed metrics and recommendations

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
dataYes
summaryYes
recommendationsNo

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed2 schema fields changedv1.0.27
    • changedInput schema / properties / categories / items / enum
      Previous value: -[
-  "performance",
-  "accessibility",
-  "best-practices",
-  "seo",
-  "pwa"
-]New value: +[
+  "performance",
+  "accessibility",
+  "best-practices",
+  "seo",
+  "agentic-browsing"
+]
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": false,
+  "properties": {
+    "data": {
+      "additionalProperties": false,
+      "properties": {
+        "differences": {
+          "additionalProperties": {
+            "additionalProperties": false,
+            "properties": {
+              "better": {
+                "enum": [
+                  "mobile",
+                  "desktop"
+                ],
+                "type": "string"
+              },
+              "desktop": {
+                "type": "number"
+              },
+              "difference": {
+                "type": "number"
+              },
+              "mobile": {
+                "type": "number"
+              }
+            },
+            "required": [
+              "mobile",
+              "desktop",
+              "difference",
+              "better"
+            ],
+            "type": "object"
+          },
+          "propertyNames": {
+            "type": "string"
+          },
+          "type": "object"
+        },
+        "includeDetails": {
+          "type": "boolean"
+        }
+      },
+      "required": [
+        "differences"
+      ],
+      "type": "object"
+    },
+    "recommendations": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "summary": {
+      "type": "string"
+    }
+  },
+  "required": [
+    "summary",
+    "data"
+  ],
+  "type": "object"
+}
  2. Addedv1.0.26
  3. Removedv1.0.1
  4. First observedv1.0.0

TDQS

A3.5/5.0
Behavior3/5

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the description does not need to restate safety. However, it adds no extra behavioral context such as how the comparison is structured, whether it returns a single report or dual reports, or any throttling implications. With annotations covering the read-only nature, the description provides marginal added value.

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

Conciseness5/5

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

A single, front-loaded sentence with zero filler. It delivers the core purpose immediately and does not elaborate unnecessarily.

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

Completeness3/5

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

The tool is simple, annotations cover safety, and an output schema exists so return format details are not required. However, the description lacks usage guidance and does not mention any special considerations (e.g., throttling, category selection) that an agent might need to know for effective invocation. It is minimally sufficient but not comprehensive.

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 description coverage is 75% (high), and all parameters have descriptive names and default values in the schema. The description adds no parameter-specific meaning beyond what the schema already provides. The baseline of 3 is appropriate.

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

Purpose5/5

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

The description states a specific action (compare) on a defined resource (website performance) between mobile and desktop devices. It clearly distinguishes itself from sibling audit tools like run_audit or get_performance_score, which focus on single-device audits or individual metric categories.

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

Usage Guidelines2/5

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

No explicit guidance is given on when to use this tool versus alternatives. It does not mention that it is the preferred tool when a mobile/desktop comparison is needed, nor does it exclude cases where a single-device audit would suffice. The usage context is only implied by the tool's name.

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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