Instruments and Tools in the Medical Evaluation of Work Capacity Abstract. In the event of absence from work due to illness or accident, the attending physician is responsible for confirming the connection between absence from work (or, if applicable, reduced performance) and a health disorder (illness or accident) and subsequently issuing a certificate of incapacity for work. The certificates have the legal status of a deed and must accordingly satisfy certain legal requirements. This article presents suitable tools and instruments for this important medical task.