You must be thinking about another browser. FireFox has a Tools menu--Safari does not. Most of the things FireFox puts under its Tools menu are found in Safari preferences.
Editing or customizing the toolbar is accessible through Safari's View menu. If you need advanced features found unde "Web Developer" in the FireFox Tools menu, you can activate Safari's "Develop" menu by doing Safari > Preferencs and selecting the "Advanced "tab. At the bottom is a checkbox to show the Develop menu.
Here is a comparison. FireFox's "Tools" menu with the web developer options expanded:

Safari's "Develop" menu after activation:
