First question, what does HR have to say about this? Have you engaged that department? Reason I ask is...often HR has organizational, individual and team developmental tools in use, and can be a primary resource for you. Additionally, if such tools are currently in use in other areas of the organization, it would be good for your staff to use the same, even if some modifications are required to address your department's functional and technical specifics.
There are solid, research-based tools on the market to address your needs, and if it's feasible for you to use them (budgets, management buy-in), I would not try to reinvent the wheel. The bonus being that these are research-based tools, i.e., they actually measure something and they actually mean something. I've seen organizations use statements such as "Helps create synergy." My response...so what? That usually has little or nothing to do with serving a customer, and it has even less to do with how well a job is accomplished.
If you must use "homegrown" criteria, I agree with Xeno, and would encourage you to write the criteria much as suggested, i.e., be sure to avoid compound criteria. For example, grouping the last two examples together ("Uses the appropriate greeting and thanks the customer for calling") would render the criteria worthless when trying to evaluate a rep who does one but not the other.