Suggest a good reason for getting experience letter from employers

[ssk0703]

Hi,

I am applying for Canadian PR through Express Entry. I want to take experience certificate from my current employer as well as my previous employers.

What should I ask them (reason) to get experience certificate in designated format which will be suitable for Canadian PR?
Because I want add my roles and responsibilities in that letter and I don't want to disclose the actual reason (i.e. for Canada PR) to them.

Please suggest a good reason.

Thanks in advance.