Which permissions/policies for IAM role to be used with CloudWatch monitoring script

Which permissions/policies for IAM role to be used with CloudWatch
monitoring script

With CloudWatch monitoring script (mon-put-instance-data.pl) it's possible
to specify a IAM role name to provide AWS credentials
(--aws-iam-role=VALUE).
I'm creating a IAM role for this purpose (to run mon-put-instance-data.pl
on an AWS instance), but which permissions / policies should I give to
this role??
Thank you for your help