Final answer:
A broker should provide an appraisal to justify the listing price on a listing agreement, as it is a professional evaluation of a property's market value.
Step-by-step explanation:
To justify the listing price on a listing agreement, a broker should provide an appraisal. An appraisal is a professional assessment of a property's value, usually performed by a licensed appraiser. This value is determined by examining various factors such as the condition of the property, comparable sales in the area, and current market trends. While a municipal assessment can offer insight into property values for tax purposes, and a pro-forma may project future income for investment properties, it is the appraisal that is most commonly used in setting a listing price for real estate sales.