Pixel - Full Control
When you want to level-up your ad tracking with Conversion API
Permission for the access token: To be able to generate an access token, an account assigned to the pixel must have full control permission, so make sure you or your client have that!
How to check if you have the right permission to the Pixel in Business Settings
No, for the pixel to fire on the browser side, you only need to pass us the Pixel ID. Chances are you also want to fire the pixel on the server side via Conversion API. In that case, you need to pass us the access token so Facebook knows we have the authority to send server events to your Pixels!