Work experience evidence under Express Entry

[adipadi]

Hi,

Whoever receives an invitation to apply for PR under Express Entry system, for prior and current work experience, does the person have to provide work experience letters which include roles and responsibilities from all prior employers, or are 'employment proof letters' sufficient, which usually just state that the person worked for the company from XXX date to YYY date?

Can someone please provide some additional info on this? Thanks!