Chrome DevTools MCP

/** * @license * Copyright 2025 Google LLC * SPDX-License-Identifier: Apache-2.0 */ import {logger} from '../logger.js'; import {DevTools} from '../third_party/index.js'; const engine = DevTools.TraceEngine.TraceModel.Model.createWithAllHandlers(); export interface TraceResult { parsedTrace: DevTools.TraceEngine.TraceModel.ParsedTrace; insights: DevTools.TraceEngine.Insights.Types.TraceInsightSets | null; } export function traceResultIsSuccess( x: TraceResult | TraceParseError, ): x is TraceResult { return 'parsedTrace' in x; } export interface TraceParseError { error: string; } export async function parseRawTraceBuffer( buffer: Uint8Array<ArrayBufferLike> | undefined, ): Promise<TraceResult | TraceParseError> { engine.resetProcessor(); if (!buffer) { return { error: 'No buffer was provided.', }; } const asString = new TextDecoder().decode(buffer); if (!asString) { return { error: 'Decoding the trace buffer returned an empty string.', }; } try { const data = JSON.parse(asString) as | { traceEvents: DevTools.TraceEngine.Types.Events.Event[]; } | DevTools.TraceEngine.Types.Events.Event[]; const events = Array.isArray(data) ? data : data.traceEvents; await engine.parse(events); const parsedTrace = engine.parsedTrace(); if (!parsedTrace) { return { error: 'No parsed trace was returned from the trace engine.', }; } const insights = parsedTrace?.insights ?? null; return { parsedTrace, insights, }; } catch (e) { const errorText = e instanceof Error ? e.message : JSON.stringify(e); logger(`Unexpected error parsing trace: ${errorText}`); return { error: errorText, }; } } const extraFormatDescriptions = `Information on performance traces may contain main thread activity represented as call frames and network requests. ${DevTools.PerformanceTraceFormatter.callFrameDataFormatDescription} ${DevTools.PerformanceTraceFormatter.networkDataFormatDescription}`; export function getTraceSummary(result: TraceResult): string { const focus = DevTools.AgentFocus.fromParsedTrace(result.parsedTrace); const formatter = new DevTools.PerformanceTraceFormatter(focus); const summaryText = formatter.formatTraceSummary(); return `## Summary of Performance trace findings: ${summaryText} ## Details on call tree & network request formats: ${extraFormatDescriptions}`; } export type InsightName = keyof DevTools.TraceEngine.Insights.Types.InsightModels; export type InsightOutput = {output: string} | {error: string}; export function getInsightOutput( result: TraceResult, insightSetId: string, insightName: InsightName, ): InsightOutput { if (!result.insights) { return { error: 'No Performance insights are available for this trace.', }; } const insightSet = result.insights.get(insightSetId); if (!insightSet) { return { error: 'No Performance Insights for the given insight set id. Only use ids given in the "Available insight sets" list.', }; } const matchingInsight = insightName in insightSet.model ? insightSet.model[insightName] : null; if (!matchingInsight) { return { error: `No Insight with the name ${insightName} found. Double check the name you provided is accurate and try again.`, }; } const formatter = new DevTools.PerformanceInsightFormatter( DevTools.AgentFocus.fromParsedTrace(result.parsedTrace), matchingInsight, ); return {output: formatter.formatInsight()}; }