It is a tool which fans can use to design and develop their own missions or racing contests. The creation will be shared on Rockstar’s Social Club for others to try on.
While the concept sounds interesting, giving the players the right to create their own content will lead to more glitches, bugs and cheaters in the GTA 5. Then again, it is something very new and free.
As for the heist missions for GTA Online, it will have to wait. After all, Rockstar did reveal that it will only come in 2014.