If you want to work at Facebook, you need to be someone that CEO Mark Zuckerberg would work for, the social networking titan said Wednesday. The Facebook chief revealed his one rule for hiring while speaking at a town-hall style session at the Mobile World Congress in Barcelona.

“I will only hire someone to work directly for me if I would work for that person,” Zuckerberg told the audience, according to the Telegraph. “It's a pretty good test and I think this rule has served me well.” Speaking with Facebook Chief Operating Officer Sheryl Sandberg, Zuckerberg implied that she had passed the test, describing her as a mentor who had helped build the company into a “healthy organization,” the Independent reported.

Zuckerberg took questions from the audience, CNN Money reported, responding to queries about how Facebook deals with foreign governments that request for content to be censored; how the company deals with hate speech; and about his philosophy regarding delegation.

On the last question, he reportedly said: “The most important thing is to keep your team as small as possible. ... Big companies get bloated.”

However, not everyone in the audience appeared to be fully engaged with the technology titan's presentation. Some social media users posted pictures of what appeared to be empty seats and audience members sleeping during the event.

Zuckerberg, 30, founded Facebook in 2004, while studying at Harvard. He advised those in the audience hoping to emulate his success to "just have faith in yourself and trust yourself.”