WebScout MCP

Instructions

Implementation Reference

• src/tools/networkCapture.js:19-192 (handler)

  The core handler function that initializes network capture by setting up Chrome DevTools Protocol (CDP) listeners for Network.requestWillBeSent, Network.responseReceived, WebSocket frames, etc. Stores captured data in session.networkCapture and enables Network/Fetch domains.
  export async function startNetworkCapture(sessionId, options = {}) { const session = global.activeSessions?.get(sessionId); if (!session) { throw new Error( `Session ${sessionId} not found. Call initializeSession first.` ); } const { capturePostOnly = false, captureStreaming = false, urlFilters = [], maxCaptures = 100, } = options; // Initialize capture storage const captureData = { sessionId, startTime: Date.now(), requests: [], responses: [], wsFrames: [], streamingResponses: [], options: { capturePostOnly, captureStreaming, urlFilters, maxCaptures }, }; // Store capture data in session session.networkCapture = captureData; // Set up CDP session for network monitoring const client = await session.context.newCDPSession(session.page); await client.send("Network.enable"); await client.send("Fetch.enable", { patterns: [{ requestStage: "Response" }], }); // Store client reference for cleanup captureData.cdpClient = client; // Network request capture client.on("Network.requestWillBeSent", (params) => { try { const { requestId, request, timestamp } = params; // Apply filters if (capturePostOnly && request.method !== "POST") return; if ( urlFilters.length > 0 && !urlFilters.some((pattern) => request.url.includes(pattern)) ) return; const requestData = { requestId, url: request.url, method: request.method, timestamp, headers: request.headers, postData: request.postData || null, }; captureData.requests.push(requestData); // Limit storage if (captureData.requests.length > maxCaptures) { captureData.requests.shift(); } } catch (e) { // Ignore capture errors } }); // Network response capture client.on("Network.responseReceived", async (params) => { try { const { requestId, response } = params; const matchingRequest = captureData.requests.find( (r) => r.requestId === requestId ); if (!matchingRequest) return; // Apply streaming filter if enabled if (captureStreaming) { const isStreaming = NetworkUtilities.isStreamingHeaders(response.headers) || response.mimeType?.includes("stream") || response.headers["transfer-encoding"] === "chunked"; if (!isStreaming) return; } const responseData = { requestId, url: response.url, status: response.status, statusText: response.statusText, headers: response.headers, mimeType: response.mimeType, timestamp: Date.now(), }; // Try to capture response body for small responses if ( response.headers["content-length"] && parseInt(response.headers["content-length"]) < 10000 ) { try { const body = await client.send("Network.getResponseBody", { requestId, }); responseData.body = body.body; responseData.base64Encoded = body.base64Encoded; } catch (e) { // Body capture failed, continue without it } } captureData.responses.push(responseData); // Limit storage if (captureData.responses.length > maxCaptures) { captureData.responses.shift(); } } catch (e) { // Ignore capture errors } }); // WebSocket frame capture client.on("Network.webSocketFrameReceived", (params) => { try { const frameData = { timestamp: Date.now(), type: "received", opcode: params.response.opcode, payload: params.response.payloadData, }; captureData.wsFrames.push(frameData); if (captureData.wsFrames.length > maxCaptures) { captureData.wsFrames.shift(); } } catch (e) { // Ignore capture errors } }); client.on("Network.webSocketFrameSent", (params) => { try { const frameData = { timestamp: Date.now(), type: "sent", opcode: params.response.opcode, payload: params.response.payloadData, }; captureData.wsFrames.push(frameData); if (captureData.wsFrames.length > maxCaptures) { captureData.wsFrames.shift(); } } catch (e) { // Ignore capture errors } }); return { sessionId, captureId: `capture_${Date.now()}`, status: "active", options: captureData.options, message: "Network capture started successfully", }; }
• src/index.js:305-347 (schema)

  Input schema definition for the tool, specifying parameters like sessionId (required) and options object with capturePostOnly, captureStreaming, urlFilters, maxCaptures.
  name: "start_network_capture", description: "Start capturing network traffic on the current browser session. Monitors all HTTP requests and responses, WebSocket frames, and streaming data. Can filter by POST requests only, streaming responses only, or specific URL patterns. Essential for analyzing API calls, debugging network issues, or monitoring real-time data flows.", inputSchema: { type: "object", properties: { sessionId: { type: "string", description: "Session ID obtained from initialize_session", }, options: { type: "object", description: "Optional capture configuration", properties: { capturePostOnly: { type: "boolean", description: "Only capture POST requests (default: false)", default: false, }, captureStreaming: { type: "boolean", description: "Only capture streaming responses (default: false)", default: false, }, urlFilters: { type: "array", items: { type: "string" }, description: "Array of URL patterns to filter captures (default: [])", default: [], }, maxCaptures: { type: "number", description: "Maximum number of captures to store (default: 100)", default: 100, }, }, }, }, required: ["sessionId"], },
• src/index.js:555-564 (registration)

  Registration in the tool dispatch switch statement in CallToolRequestSchema handler, which calls the startNetworkCapture function with extracted arguments.
  case "start_network_capture": { const { sessionId, options = {} } = args; if (!sessionId) { throw new McpError( ErrorCode.InvalidParams, "sessionId parameter is required" ); } result = await startNetworkCapture(sessionId, options); break;
• src/tools/reverseEngineer.js:22-27 (registration)

  Re-export of the startNetworkCapture function from networkCapture.js, making it available for import in index.js.
  export { startNetworkCapture, stopNetworkCapture, getNetworkCaptureStatus, clearNetworkCapture, } from "./networkCapture.js";
• src/index.js:22-26 (registration)

  Import of startNetworkCapture from reverseEngineer.js barrel export into the main index.js for use in tool handlers.
  startNetworkCapture, stopNetworkCapture, getNetworkCaptureStatus, clearNetworkCapture, } from "./tools/reverseEngineer.js";