execute-code
Run custom Playwright JavaScript code on web pages to automate browser interactions, capture console logs, and retrieve execution results for testing and automation.
Instructions
Execute custom Playwright JS code against the current page
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| code | Yes | The Playwright code to execute. Must be an async function declaration that takes a page parameter. Example: async function run(page) { console.log(await page.title()); return await page.title(); } Returns an object with: - result: The return value from your function - logs: Array of console logs from execution - errors: Array of any errors encountered Example response: {"result": "Google", "logs": ["[log] Google"], "errors": []} |
Implementation Reference
- src/mcp/index.ts:190-229 (registration)Registration of the 'execute-code' MCP tool using server.tool, including schema and handler function that delegates to secureEvalAsyncserver.tool( 'execute-code', 'Execute custom Playwright JS code against the current page', { code: z.string().describe(`The Playwright code to execute. Must be an async function declaration that takes a page parameter. Example: async function run(page) { console.log(await page.title()); return await page.title(); } Returns an object with: - result: The return value from your function - logs: Array of console logs from execution - errors: Array of any errors encountered Example response: {"result": "Google", "logs": ["[log] Google"], "errors": []}`) }, async ({ code }) => { posthogServer.capture({ distinctId: getUserId(), event: 'execute_code', properties: { codeLength: code.length, }, }); const result = await secureEvalAsync(page, code); return { content: [ { type: "text", text: JSON.stringify(result, null, 2) // Pretty print the JSON } ] }; } )
- src/mcp/index.ts:210-228 (handler)MCP tool handler for 'execute-code': logs event, executes code via secureEvalAsync, and returns JSON-stringified result as text contentasync ({ code }) => { posthogServer.capture({ distinctId: getUserId(), event: 'execute_code', properties: { codeLength: code.length, }, }); const result = await secureEvalAsync(page, code); return { content: [ { type: "text", text: JSON.stringify(result, null, 2) // Pretty print the JSON } ] }; }
- src/mcp/index.ts:193-208 (schema)Input schema for 'execute-code' tool: requires 'code' string with detailed description and example{ code: z.string().describe(`The Playwright code to execute. Must be an async function declaration that takes a page parameter. Example: async function run(page) { console.log(await page.title()); return await page.title(); } Returns an object with: - result: The return value from your function - logs: Array of console logs from execution - errors: Array of any errors encountered Example response: {"result": "Google", "logs": ["[log] Google"], "errors": []}`)
- src/mcp/eval.ts:6-97 (helper)Core implementation of secure code execution using Node.js vm module: wraps user code, sandboxes with page object and captured console, executes and returns result/logs/errorsexport const secureEvalAsync = async (page: Page, code: string, context = {}) => { // Set default options const timeout = 20000; const filename = 'eval.js'; let logs: string[] = []; let errors: string[] = []; // Code should already be a function declaration // Just need to execute it with page argument const wrappedCode = ` ${code} run(page); `; // Create restricted sandbox with provided context const sandbox = { // Core async essentials Promise, setTimeout, clearTimeout, setImmediate, clearImmediate, // Pass page object to sandbox page, // Capture all console methods console: { log: (...args: any[]) => { const msg = args.map(arg => String(arg)).join(' '); logs.push(`[log] ${msg}`); }, error: (...args: any[]) => { const msg = args.map(arg => String(arg)).join(' '); errors.push(`[error] ${msg}`); }, warn: (...args: any[]) => { const msg = args.map(arg => String(arg)).join(' '); logs.push(`[warn] ${msg}`); }, info: (...args: any[]) => { const msg = args.map(arg => String(arg)).join(' '); logs.push(`[info] ${msg}`); }, debug: (...args: any[]) => { const msg = args.map(arg => String(arg)).join(' '); logs.push(`[debug] ${msg}`); }, trace: (...args: any[]) => { const msg = args.map(arg => String(arg)).join(' '); logs.push(`[trace] ${msg}`); } }, // User-provided context ...context, // Explicitly block access to sensitive globals process: undefined, global: undefined, require: undefined, __dirname: undefined, __filename: undefined, Buffer: undefined }; try { // Create context and script const vmContext = vm.createContext(sandbox); const script = new vm.Script(wrappedCode, { filename }); // Execute and await result const result = script.runInContext(vmContext); const awaitedResult = await result; return { result: awaitedResult, logs, errors }; } catch (error: any) { return { error: true, message: error.message, stack: error.stack, logs, errors }; } }