execute-code
Execute custom Playwright JavaScript code to interact with web pages, retrieve page data, perform automated actions, and capture console logs and execution results for browser automation tasks.
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:210-229 (handler)The handler function for the 'execute-code' tool. It captures analytics, executes the user-provided code securely using secureEvalAsync, and returns the result as pretty-printed JSON text content.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:193-209 (schema)Input schema definition using Zod for the 'code' parameter, including detailed usage instructions 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/index.ts:190-229 (registration)Complete registration of the 'execute-code' tool using server.tool, specifying name, description, input schema, and handler function.server.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/eval.ts:5-97 (helper)Core helper function secureEvalAsync that executes the code in a sandboxed VM context, providing the page object, capturing console output and errors, and blocking sensitive globals.// Not super secure, but it's ok for now export 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 }; } }