puppeteer_evaluate

Instructions

Implementation Reference

• src/tools/definitions.ts:94-104 (schema)

  Schema definition for the puppeteer_evaluate tool. It has name 'puppeteer_evaluate', description 'Execute JavaScript in the browser console', and expects a required 'script' string parameter as input.

  {
    name: "puppeteer_evaluate",
    description: "Execute JavaScript in the browser console",
    inputSchema: {
      type: "object",
      properties: {
        script: { type: "string", description: "JavaScript code to execute" },
      },
      required: ["script"],
    },
  },

• src/tools/handlers.ts:224-273 (handler)

  Handler implementation for puppeteer_evaluate. Sets up console listener, executes the provided JavaScript via page.evaluate() wrapped in an async IIFE, captures console output, and returns both the result and console logs.

  case "puppeteer_evaluate":
    try {
      // Set up console listener
      const logs: string[] = [];
      const consoleListener = (message: any) => {
        logs.push(`${message.type()}: ${message.text()}`);
      };
      
      page.on('console', consoleListener);
      
      // Execute script with proper serialization
      logger.debug('Executing script in browser', { scriptLength: args.script.length });
      
      // Wrap the script in a function that returns a serializable result
      const result = await page.evaluate(`(async () => {
        try {
          const result = (function() { ${args.script} })();
          return result;
        } catch (e) {
          console.error('Script execution error:', e.message);
          return { error: e.message };
        }
      })()`);
      
      // Remove the listener to avoid memory leaks
      page.off('console', consoleListener);
      
      logger.debug('Script execution result', {
        resultType: typeof result,
        hasResult: result !== undefined,
        logCount: logs.length
      });
  
      return {
        content: [{
          type: "text",
          text: `Execution result:\n${JSON.stringify(result, null, 2)}\n\nConsole output:\n${logs.join('\n')}`,
        }],
        isError: false,
      };
    } catch (error) {
      logger.error('Script evaluation failed', { error: error instanceof Error ? error.message : String(error) });
      return {
        content: [{
          type: "text",
          text: `Script execution failed: ${error instanceof Error ? error.message : String(error)}\n\nPossible causes:\n- Syntax error in script\n- Execution timeout\n- Browser security restrictions\n- Serialization issues with complex objects`,
        }],
        isError: true,
      };
    }

• src/server.ts:35-41 (registration)

  Tool registration in the server. The ListToolsRequestSchema handler exposes TOOLS (which includes puppeteer_evaluate), and the CallToolRequestSchema handler dispatches to handleToolCall which contains the case for 'puppeteer_evaluate'.

  server.setRequestHandler(ListToolsRequestSchema, async () => ({
    tools: TOOLS,
  }));
  
  server.setRequestHandler(CallToolRequestSchema, async (request) =>
    handleToolCall(request.params.name, request.params.arguments ?? {}, state, server)
  );