Firefox Extension: Create a new tab and operate with this tab only?

I create a tab in Firefox and load a url:

function createNewEbayTab()
{
    newTab = browser.tabs.create({
    active: false,
    url:"https://www.google.de"
  });
};

Now I would like to open every further URL that I call within the extension in this tab. What is the best way to do this?

Thanks!