chrome-devtools

# Chrome DevTools Agent ## Overview A specialized skill for controlling and inspecting a live Chrome browser. This skill leverages the `chrome-devtools` MCP server to perform a wide range of browser-related tasks, from simple navigation to complex performance profiling. ## When to Use Use this skill when: - **Browser Automation**: Navigating pages, clicking elements, filling forms, and handling dialogs. - **Visual Inspection**: Taking screenshots or text snapshots of web pages. - **Debugging**: Inspecting console messages, evaluating JavaScript in the page context, and analyzing network requests. - **Performance Analysis**: Recording and analyzing performance traces to identify bottlenecks and Core Web Vital issues. - **Emulation**: Resizing the viewport or emulating network/CPU conditions. ## Tool Categories ### 1. Navigation & Page Management - `new_page`: Open a new tab/page. - `navigate_page`: Go to a specific URL, reload, or navigate history. - `select_page`: Switch context between open pages. - `list_pages`: See all open pages and their IDs. - `close_page`: Close a specific page. - `wait_for`: Wait for specific text to appear on the page. ### 2. Input & Interaction - `click`: Click on an element (use `uid` from snapshot). - `fill` / `fill_form`: Type text into inputs or fill multiple fields at once. - `hover`: Move the mouse over an element. - `press_key`: Send keyboard shortcuts or special keys (e.g., "Enter", "Control+C"). - `drag`: Drag and drop elements. - `handle_dialog`: Accept or dismiss browser alerts/prompts. - `upload_file`: Upload a file through a file input. ### 3. Debugging & Inspection - `take_snapshot`: Get a text-based accessibility tree (best for identifying elements). - `take_screenshot`: Capture a visual representation of the page or a specific element. - `list_console_messages` / `get_console_message`: Inspect the page's console output. - `evaluate_script`: Run custom JavaScript in the page context. - `list_network_requests` / `get_network_request`: Analyze network traffic and request details. ### 4. Emulation & Performance - `resize_page`: Change the viewport dimensions. - `emulate`: Throttling CPU/Network or emulating geolocation. - `performance_start_trace`: Start recording a performance profile. - `performance_stop_trace`: Stop recording and save the trace. - `performance_analyze_insight`: Get detailed analysis from recorded performance data. ## Workflow Patterns ### Pattern A: Identifying Elements (Snapshot-First) Always prefer `take_snapshot` over `take_screenshot` for finding elements. The snapshot provides `uid` values which are required by interaction tools. ```markdown 1. `take_snapshot` to get the current page structure. 2. Find the `uid` of the target element. 3. Use `click(uid=...)` or `fill(uid=..., value=...)`. ``` ### Pattern B: Troubleshooting Errors When a page is failing, check both console logs and network requests. ```markdown 1. `list_console_messages` to check for JavaScript errors. 2. `list_network_requests` to identify failed (4xx/5xx) resources. 3. `evaluate_script` to check the value of specific DOM elements or global variables. ``` ### Pattern C: Performance Profiling Identify why a page is slow. ```markdown 1. `performance_start_trace(reload=true, autoStop=true)` 2. Wait for the page to load/trace to finish. 3. `performance_analyze_insight` to find LCP issues or layout shifts. ``` ## Best Practices - **Context Awareness**: Always run `list_pages` and `select_page` if you are unsure which tab is currently active. - **Snapshots**: Take a new snapshot after any major navigation or DOM change, as `uid` values may change. - **Timeouts**: Use reasonable timeouts for `wait_for` to avoid hanging on slow-loading elements. - **Screenshots**: Use `take_screenshot` sparingly for visual verification, but rely on `take_snapshot` for logic.