The Tesla robot is a Vault-Tec security robot model implemented in the company's Secret Vault. Like its fellow security robots, it is a three-legged orb-like walker. Tesla robots use powerful electric blasts generated by special Tesla device mounted on them to attack possible threats to the well-being of the Vault. However, no security robots could protect the Secret Vault from an army of super mutants.
Vault-Tec also developed a special bodyguard programming called "Mr. Buddy" for Tesla robots, probably to help scientists from the laboratories to feel much more safe when going up into Wasteland or doing research on living subjects. However, "Mr. Buddy" was never finished and left in Beta state.
This one is a prototype, improved model of Tesla robot. Surprisingly, it's even smaller than normal Tesla robots, only a bit bigger than service robot. But the MK-X is the strongest of them and could obliterate many super mutants in few seconds.