WebAPI Blocker is a lite addon that lets you easily block and nullify a desired web API.
Simply open the toolbar popup UI and choose an API from the drop-down list. Then, click on the (+) button to add the item to the API list. Once you add an item, you can remove it from the list by clicking on the "remove" button next to each item. Moreover, you can deactivate an item by removing the check-mark from the list. There is also a "reload" button at the top toolbar to reload the active tab.
Note: please be careful when you block (nullify) a web API. Because certain API(s) may cause websites to not fully load or even make them unresponsive. Therefore, please do enough research before disabling an API.
To report bugs, please fill the bug report form in the addon's homepage (https://mybrowseraddon.com/webapi-blocker.html).