The Agent is only bothered about the TV show and not about the real lives of Bolt, Penny, or her mother to the extent that he is unsympathetic, abrupt, and a bit greedy for money. When Bolt goes missing, the Agent even goes as far as to try and force Penny to go on with the show with a dog resembling Bolt. He even tries to exploit Penny's near death experience from the fire for his own gain, which promptly results in his downfall.
The Agent's job is to control Penny to keep her working for the TV show, no matter what. He also tries to lure her away from Bolt, describing the studio as Bolt's "world".
When Bolt disappears, he wants Penny to work with another dog.
During the fire on the set, the Agent re-encounters the real Bolt, tripping over the dog while fleeing.
After Penny and Bolt are rescued from the fire and taken into an ambulance with her mother, the Agent joins them and tells Penny's mother that Penny could still do the show even when injured so he can earn money. He is immediately thrown out of the ambulance by Penny's outraged mother, who announces to him that she, Penny, and Bolt quit. He tries to talk them out of it with his signature "pin" move, but Penny's mother, fed up with his smooth talk, slams the ambulance door in his face. He presumably becomes the agent of Penny's replacement afterwards or he got fired.
His catchphrase is "Let's put a pin in it," which he uses to end conversations states he would rather not discuss further.
Character Development Art of The Agent (below) depicted him as more sinister and shark-like.
In fact, Joe Moshier (a character design artist of the film) stated in The Art of Bolt that he studied sharks when he was developing the character and wanted to give him a shark-like quality to communicate visually that he shouldn't be trusted.
Character Development Art of The Agent by Joe Moshier