Final answer:
A written agency agreement is not mandated by law in general, but specific jurisdictions or company policies might require it for certain transactions. It provides clarity and legal protection for the parties involved.
Step-by-step explanation:
A written agency agreement is not required by law but may be required by company policy. Agency relationships can often be formed by oral agreement or through the actions of the parties involved. However, some jurisdictions require written agreements for certain types of transactions, for example, the sale of real estate. Companies may also have their own policies requiring written agreements to ensure clarity and protect the interests of all parties.