Half-Life 2 Tools for Garry's Mod Sandbox
Half-Life 2 related tools for Garry's Mod Sandbox gamemode
Installation
You do not need to download and install this addon manually, it is available on the Steam Workshop: https://steamcommunity.com/sharedfiles/filedetails/?id=104619813
Simply press the green + Subscribe button on the addon page and it will be automatically downloaded when you next start Garry's Mod.