There are a few restrictions on what add-ons can do. Improve your users' overall experience by avoiding these pitfalls.
The following restrictions apply to all add-ons. Don't do the following:
Change features in G Suite
The Add-ons framework is designed to enhance G Suite applications—not to add limits. Consequently, you can't alter existing features or lock down the G Suite document sharing model.
Charge users to install
We don't provide a way to charge users for installing add-ons, and add-ons can't include ads. However, you can roll your own payment system or call into an existing billing database. Your add-on can connect to non-Google services that bill users.
Detect many events
Except for certain triggers, add-ons can't tell what a user does outside the add-on itself. For example, you can't detect when the user clicks on the Google Docs toolbar. It is possible to poll for changes in a file's contents from a sidebar's client-side code, although you'll always have a slight delay.
The following restrictions only apply to Gmail add-ons and the use of the Card service. Don't do the following:
Develop Gmail add-ons for iOS
Gmail add-ons have not yet been added to the iOS version of the Gmail app.
Change features in Gmail
The add-ons framework is designed to enhance Gmail—not to add limits. Consequently, you can't alter existing features or the Gmail user interface.
Use client-side scripting
Use Apps Script triggers
Use SVG Images
You can't currently use SVG images with Card service widgets.
Have more than 100 widgets
For performance reasons, you can't add more than 100 widgets to a card section.