Launching tools directly
From Valve Developer Community
Most SDK tools, including Hammer and its compilers, HLMV, and Faceposer do not work properly when run by double clicking on them as an EXE. A quick way to solve this issue is to create a shortcut or a batch file that runs the EXE with the parameter -game ../yourmod. Depending on the game, -nop4 may also be required to prevent crashes.
