browsercat_evaluate
Execute JavaScript code directly in a browser console to automate web interactions, extract data, or test functionality through cloud-based browsing.
Instructions
Execute JavaScript in the browser console
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| script | Yes | JavaScript code to execute |
Implementation Reference
- index.ts:304-348 (handler)Handler function for 'browsercat_evaluate' tool. Evaluates the provided JavaScript script in the browser page, temporarily overrides console methods to capture logs, restores console, and returns the result with captured console output.
case "browsercat_evaluate": try { // Set up console log capture await page.evaluate(() => { window.mcpHelper = { logs: [], originalConsole: { ...console }, }; ['log', 'info', 'warn', 'error'].forEach(method => { (console as any)[method] = (...args: any[]) => { window.mcpHelper.logs.push(`[${method}] ${args.join(' ')}`); (window.mcpHelper.originalConsole as any)[method](...args); }; }); }); const result = await page.evaluate(args.script); // Restore original console and get captured logs const logs = await page.evaluate(() => { Object.assign(console, window.mcpHelper.originalConsole); const logs = window.mcpHelper.logs; delete (window as any).mcpHelper; return logs; }); return { content: [ { type: "text", text: `Execution result:\n${JSON.stringify(result, null, 2)}\n\nConsole output:\n${logs.join('\n')}`, }, ], isError: false, }; } catch (error) { return { content: [{ type: "text", text: `Script execution failed: ${(error as Error).message}`, }], isError: true, }; } - index.ts:100-110 (schema)Tool definition including name, description, and input schema for 'browsercat_evaluate'.
{ name: "browsercat_evaluate", description: "Execute JavaScript in the browser console", inputSchema: { type: "object", properties: { script: { type: "string", description: "JavaScript code to execute" }, }, required: ["script"], }, }, - index.ts:421-423 (registration)MCP server request handler for listing tools, which includes 'browsercat_evaluate' from the TOOLS array.
server.setRequestHandler(ListToolsRequestSchema, async () => ({ tools: TOOLS, })); - index.ts:425-427 (registration)MCP server request handler for calling tools, which dispatches to handleToolCall based on the tool name 'browsercat_evaluate'.
server.setRequestHandler(CallToolRequestSchema, async (request) => handleToolCall(request.params.name, request.params.arguments ?? {}) );