MCP Web Research Server

Instructions

Input Schema

Input Schema (JSON Schema)

Implementation Reference

• index.ts:1056-1113 (handler)

  Main handler for the 'take_screenshot' tool within the CallToolRequestSchema switch statement. Captures screenshot using helper function, saves it, stores in session, notifies resource change, and returns URI for viewing.
  case "take_screenshot": { try { // Step 1: Capture screenshot with retry mechanism const screenshot = await withRetry(async () => { // Take and optimize screenshot with default size limits return await takeScreenshotWithSizeLimit(page); }); // Step 2: Initialize session if needed if (!currentSession) { currentSession = { query: "Screenshot Session", // Session identifier results: [], // Empty results array lastUpdated: new Date().toISOString(), // Current timestamp }; } // Step 3: Get current page information const pageUrl = await page.url(); // Current page URL const pageTitle = await page.title(); // Current page title // Step 4: Save screenshot to disk const screenshotPath = await saveScreenshot(screenshot, pageTitle || 'untitled'); // Step 5: Create and store screenshot result const resultIndex = currentSession ? currentSession.results.length : 0; addResult({ url: pageUrl, title: pageTitle || "Untitled Page", // Fallback title if none available content: "Screenshot taken", // Simple content description timestamp: new Date().toISOString(), // Capture time screenshotPath // Path to screenshot file }); // Step 6: Notify clients about new screenshot resource server.notification({ method: "notifications/resources/list_changed" }); // Step 7: Return success message with resource URI const resourceUri = `research://screenshots/${resultIndex}`; return { content: [{ type: "text" as const, text: `Screenshot taken successfully. You can view it via *MCP Resources* (Paperclip icon) @ URI: ${resourceUri}` }] }; } catch (error) { // Handle and format screenshot errors return { content: [{ type: "text" as const, text: `Failed to take screenshot: ${(error as Error).message}` }], isError: true }; } }
• index.ts:479-562 (helper)

  Helper function that performs the actual screenshot capture using Playwright's page.screenshot(). Optimizes size by resizing viewport if necessary to stay under 5MB limit. Returns base64 PNG data.
  async function takeScreenshotWithSizeLimit(page: Page): Promise<string> { const MAX_SIZE = 5 * 1024 * 1024; const MAX_DIMENSION = 1920; const MIN_DIMENSION = 800; // Set viewport size await page.setViewportSize({ width: 1600, height: 900 }); // Take initial screenshot let screenshot = await page.screenshot({ type: 'png', fullPage: false }); // Handle buffer conversion let buffer = screenshot; let attempts = 0; const MAX_ATTEMPTS = 3; // While screenshot is too large, reduce size while (buffer.length > MAX_SIZE && attempts < MAX_ATTEMPTS) { // Get current viewport size const viewport = page.viewportSize(); if (!viewport) continue; // Calculate new dimensions const scaleFactor = Math.pow(0.75, attempts + 1); let newWidth = Math.round(viewport.width * scaleFactor); let newHeight = Math.round(viewport.height * scaleFactor); // Ensure dimensions are within bounds newWidth = Math.max(MIN_DIMENSION, Math.min(MAX_DIMENSION, newWidth)); newHeight = Math.max(MIN_DIMENSION, Math.min(MAX_DIMENSION, newHeight)); // Update viewport with new dimensions await page.setViewportSize({ width: newWidth, height: newHeight }); // Take new screenshot screenshot = await page.screenshot({ type: 'png', fullPage: false }); // Update buffer with new screenshot buffer = screenshot; // Increment retry attempts attempts++; } // Final attempt with minimum settings if (buffer.length > MAX_SIZE) { await page.setViewportSize({ width: MIN_DIMENSION, height: MIN_DIMENSION }); // Take final screenshot screenshot = await page.screenshot({ type: 'png', fullPage: false }); // Update buffer with final screenshot buffer = screenshot; // Throw error if final screenshot is still too large if (buffer.length > MAX_SIZE) { throw new McpError( ErrorCode.InvalidRequest, `Failed to reduce screenshot to under 5MB even with minimum settings` ); } } // Convert Buffer to base64 string before returning return buffer.toString('base64'); }
• index.ts:156-163 (registration)

  Tool registration entry in the TOOLS array, which is returned by ListToolsRequestHandler. Defines name, description, and empty input schema (no params required).
  { name: "take_screenshot", description: "Take a screenshot of the current page", inputSchema: { type: "object", properties: {}, // No parameters needed }, },
• index.ts:156-163 (schema)

  Input schema definition for the 'take_screenshot' tool: empty object (no input parameters). Part of TOOLS array.
  { name: "take_screenshot", description: "Take a screenshot of the current page", inputSchema: { type: "object", properties: {}, // No parameters needed }, },