Two things to note about this:

1. You still need a chain tool if you put on a new chain because you will need to remove links to get the right chain length.

2. For most modern chains (i.e. last 20+ years), you MUST use a quick link and must never try to join a chain with a chain tool. This is because the pins on modern chains are peened or flared at the ends. When you use a chain tool to drive out a pin the peening or flaring is torn off and the pin is ruined. If you try to reset it with the chain tool the chain will be very badly weakened at that spot and will snap when you apply high torque to it (i.e. standing on the pedals on a hill). The consequences are never good when this happens. This is the reason that all modern chains come with quick links.