Visual Snapshot Skill

Capabilities

This skill allows you to "see" the Shopify theme and interact with it programmatically. You can navigate, click, type, and execute complex JavaScript logic to verify your work.

Dependencies

• MCP Server: @modelcontextprotocol/server-playwright
• Shopify CLI: Must be running shopify theme dev to serve the site (default: http://localhost:9292).

Tools Usage Guide

1. playwright_navigate

Use this to open the local development URL.

• Param url: usually http://localhost:9292.

2. playwright_screenshot

Use this to capture the current state.

• Param name: filename prefix.
• Param selector: capture specific element.
• Param width/height: viewport dimensions.

3. playwright_evaluate (Advanced: Remote Code Execution)

This is the most powerful tool. It allows you to execute unlimited Playwright/JS code in the browser context in a SINGLE turn.

• Param script: The JavaScript code to run. Code runs inside the browser page context.
• Usage: Use this for complex interactions (loops, conditionals) or to batch multiple actions (Filling forms -> Clicking -> Waiting -> Returning data).
• Example:

  // Agent sends this string to 'script' param
  const items = document.querySelectorAll(".product-card");
  const results = [];
  for (const item of items) {
    if (item.innerText.includes("Sale")) {
      item.querySelector("button").click(); // Add to cart
      results.push(item.id);
    }
  }
  return results; // Returns data to Agent
  

Workflow: Visual Verification Loop

When asked to fix a UI bug or implement a design:

1. Analyze: Understand the request.
2. Snapshot (Before):
   • Use playwright_navigate.
   • Use playwright_screenshot.
   • Tip: Use playwright_evaluate to setup complex state (e.g., login, add item to cart) before screenshot.
   • CRITICAL: Use specific MCP tool to view the image file if not automatically shown.
3. Code: Apply fixes to Liquid/CSS.
4. Snapshot (After): Verify changes.

Advanced Pattern: "Code-as-Params"

Instead of calling click -> wait -> click (3 turns), just write a script: playwright_evaluate(script="document.getElementById('menu-toggle').click();")