get_performance_score

Analyze and retrieve the performance score of a webpage by providing its URL and device type, helping identify optimization areas using Google's Lighthouse metrics.

Instructions

Get just the performance score for a URL

Input Schema

TableJSON Schema

Name	Required	Description	Default
`device`	No	Device to emulate (defaults to mobile)
`url`	Yes	URL to audit

Implementation Reference

src/index.ts:267-314 (handler)

The primary handler function for the 'get_performance_score' tool. It validates input args, configures a performance-only Lighthouse audit, executes it via handleRunAudit, parses the result, extracts the performance score and metrics, and returns formatted JSON response.

private async handleGetPerformanceScore(args: any) {
  if (!isValidAuditArgs(args)) {
    throw new McpError(
      ErrorCode.InvalidParams,
      'Invalid performance score arguments'
    );
  }

  try {
    // Run a focused performance audit
    const auditArgs: RunAuditArgs = {
      url: args.url,
      categories: ['performance'],
      device: args.device || 'mobile',
      throttling: true,
    };

    const result = await this.handleRunAudit(auditArgs);
    
    // Extract just the performance data
    const resultData = JSON.parse(result.content[0].text);
    const performanceData = {
      url: resultData.url,
      performanceScore: resultData.scores.performance.score,
      metrics: resultData.metrics,
    };

    return {
      content: [
        {
          type: 'text',
          text: JSON.stringify(performanceData, null, 2),
        },
      ],
    };
  } catch (error: any) {
    console.error('Performance score error:', error);
    return {
      content: [
        {
          type: 'text',
          text: `Error getting performance score: ${error.message || error}`,
        },
      ],
      isError: true,
    };
  }
}

src/index.ts:117-131 (schema)

The input schema defining the expected arguments for the 'get_performance_score' tool: required 'url' string and optional 'device' enum.

inputSchema: {
  type: 'object',
  properties: {
    url: {
      type: 'string',
      description: 'URL to audit',
    },
    device: {
      type: 'string',
      enum: ['mobile', 'desktop'],
      description: 'Device to emulate (defaults to mobile)',
    },
  },
  required: ['url'],
},

src/index.ts:114-132 (registration)

Registration of the 'get_performance_score' tool in the ListToolsRequestSchema handler, including name, description, and input schema.

{
  name: 'get_performance_score',
  description: 'Get just the performance score for a URL',
  inputSchema: {
    type: 'object',
    properties: {
      url: {
        type: 'string',
        description: 'URL to audit',
      },
      device: {
        type: 'string',
        enum: ['mobile', 'desktop'],
        description: 'Device to emulate (defaults to mobile)',
      },
    },
    required: ['url'],
  },
},

src/index.ts:140-141 (registration)
Dispatch/registration of the tool handler in the switch statement within CallToolRequestSchema handler.
```
case 'get_performance_score':
  return this.handleGetPerformanceScore(request.params.arguments);
```

src/index.ts:33-46 (helper)

Helper validation function `isValidAuditArgs` used by the get_performance_score handler to validate input arguments.

const isValidAuditArgs = (args: any): args is RunAuditArgs => {
  return (
    typeof args === 'object' &&
    args !== null &&
    typeof args.url === 'string' &&
    (args.categories === undefined ||
      (Array.isArray(args.categories) &&
        args.categories.every((cat: any) => typeof cat === 'string'))) &&
    (args.device === undefined ||
      args.device === 'mobile' ||
      args.device === 'desktop') &&
    (args.throttling === undefined || typeof args.throttling === 'boolean')
  );
};

lighthouse-mcp