feat(tool): added code coverage tool

tool to analyse unused code

Author: yashverma2110

docs/tool-reference.md

@@ -21,7 +21,9 @@
 - **[Emulation](#emulation)** (2 tools)
   - [`emulate`](#emulate)
   - [`resize_page`](#resize_page)
-- **[Performance](#performance)** (3 tools)
+- **[Performance](#performance)** (5 tools)
+  - [`coverage_start`](#coverage_start)
+  - [`coverage_stop`](#coverage_stop)
   - [`performance_analyze_insight`](#performance_analyze_insight)
   - [`performance_start_trace`](#performance_start_trace)
   - [`performance_stop_trace`](#performance_stop_trace)
@@ -215,6 +217,29 @@
 
 ## Performance
 
+### `coverage_start`
+
+**Description:** Starts code coverage tracking on the selected page. This tracks which JavaScript and CSS code is actually used, helping identify unused code that could be removed to improve page performance.
+
+**Parameters:**
+
+- **includeCSS** (boolean) _(optional)_: Whether to include CSS coverage. Defaults to true.
+- **includeJS** (boolean) _(optional)_: Whether to include JavaScript coverage. Defaults to true.
+- **resetOnNavigation** (boolean) _(optional)_: Whether to reset coverage data on page navigation. Defaults to true.
+
+---
+
+### `coverage_stop`
+
+**Description:** Stops code coverage tracking and returns a comprehensive report showing URLs, total bytes, used bytes, unused bytes, and usage percentage for each JavaScript and CSS resource. Results are sorted by unused bytes (most wasted first) and paginated.
+
+**Parameters:**
+
+- **pageIdx** (integer) _(optional)_: Page index (0-based). Use this to navigate through results. For example, pageIdx: 1 shows the next page.
+- **pageSize** (integer) _(optional)_: Number of results to show per page. Maximum and default is 5 to keep output manageable.
+
+---
+
 ### `performance_analyze_insight`
 
 **Description:** Provides more detailed information on a specific Performance Insight of an insight set that was highlighted in the results of a trace recording.

src/McpContext.ts

@@ -106,6 +106,11 @@ export class McpContext implements Context {
   #consoleCollector: ConsoleCollector;
 
   #isRunningTrace = false;
+  #isRunningCoverage = false;
+  #coverageOptions: {includeJS: boolean; includeCSS: boolean} = {
+    includeJS: true,
+    includeCSS: true,
+  };
   #networkConditionsMap = new WeakMap<Page, string>();
   #cpuThrottlingRateMap = new WeakMap<Page, number>();
   #geolocationMap = new WeakMap<Page, GeolocationOptions>();
@@ -306,6 +311,22 @@ export class McpContext implements Context {
     return this.#isRunningTrace;
   }
 
+  setIsRunningCoverage(x: boolean): void {
+    this.#isRunningCoverage = x;
+  }
+
+  isRunningCoverage(): boolean {
+    return this.#isRunningCoverage;
+  }
+
+  setCoverageOptions(options: {includeJS: boolean; includeCSS: boolean}): void {
+    this.#coverageOptions = options;
+  }
+
+  getCoverageOptions(): {includeJS: boolean; includeCSS: boolean} {
+    return this.#coverageOptions;
+  }
+
   getDialog(): Dialog | undefined {
     return this.#dialog;
   }

src/tools/ToolDefinition.ts

@@ -81,11 +81,20 @@ export interface Response {
 /**
  * Only add methods required by tools/*.
  */
+export interface CoverageOptions {
+  includeJS: boolean;
+  includeCSS: boolean;
+}
+
 export type Context = Readonly<{
   isRunningPerformanceTrace(): boolean;
   setIsRunningPerformanceTrace(x: boolean): void;
   recordedTraces(): TraceResult[];
   storeTraceRecording(result: TraceResult): void;
+  isRunningCoverage(): boolean;
+  setIsRunningCoverage(x: boolean): void;
+  getCoverageOptions(): CoverageOptions;
+  setCoverageOptions(options: CoverageOptions): void;
   getSelectedPage(): Page;
   getDialog(): Dialog | undefined;
   clearDialog(): void;