Here's an example of a clause that could be added to an appointment letter to specify the appraisal cycle and eligibility for appraisal:
"Appraisal Cycle and Eligibility: The employee will be eligible for an annual performance appraisal, conducted on a [specify time frame, e.g., calendar year] basis. The initial appraisal will be conducted after completion of [specify time frame, e.g., one year] of continuous employment with the company. Subsequent appraisals will be conducted annually thereafter. The specific dates and timelines for the appraisal cycle will be communicated to the employee by the Human Resources department. The appraisal process will assess the employee's performance, achievements, and contributions to the organization during the specified evaluation period. The results of the appraisal may be used as a basis for performance-related decisions, including compensation adjustments, promotions, and employee development plans."
It's important to note that this is just an example, and you may need to tailor it to suit your organization's specific policies and practices. Additionally, you should consult with legal and HR professionals to ensure compliance with local laws and regulations.