evaluate_javascript
Execute custom JavaScript code within a browser context using the MCP Browser Server, enabling automation for web interactions, data extraction, and dynamic content manipulation.
Instructions
Execute JavaScript in the browser context
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| script | Yes | JavaScript code to execute |
Implementation Reference
- src/index.ts:583-599 (handler)The handler function for evaluate_javascript tool. It checks for currentPage, parses args with schema, evaluates the JS script on the page using Playwright's evaluate method, and returns the result as JSON stringified text.case 'evaluate_javascript': { if (!currentPage) { throw new Error('No browser page available. Launch a browser first.'); } const params = EvaluateJavaScriptSchema.parse(args); const result = await currentPage.evaluate(params.script); return { content: [ { type: 'text', text: `JavaScript result: ${JSON.stringify(result, null, 2)}` } ] }; }
- src/index.ts:55-57 (schema)Defines the input schema for the evaluate_javascript tool using Zod, requiring a 'script' string.const EvaluateJavaScriptSchema = z.object({ script: z.string() });
- src/index.ts:281-294 (registration)Registers the evaluate_javascript tool in the list of available tools, including name, description, and input schema.{ name: 'evaluate_javascript', description: 'Execute JavaScript in the browser context', inputSchema: { type: 'object', properties: { script: { type: 'string', description: 'JavaScript code to execute' } }, required: ['script'] } },