Is there a way to restrict which functions could be called through google.script.run?

Question

I just deployed my first google apps script web app. However, I'm concerned about all the functions defined in the code.gs. They could be called by anyone with access to the dev console in chrome. They could call google.script.run on any of them.

Some of those functions are there only as a foundation to use in other functions (example below). Is there a way to restrict which functions could be called through google.script.run?

function openRentManagerDatabase (spreaSheetId) {
    return SpreadsheetApp.openByIspreadsheetId);
}