According to the AGA (Association of Government Accountants) Code of Ethics, a government agency contract manager using a vendor as a personal reference would indeed constitute a conflict of interest.
A conflict of interest occurs when an individual's personal interests or relationships could potentially influence their professional judgment or decision-making. In this case, the contract manager using a vendor as a personal reference suggests a close personal relationship or connection between the two parties. By using the vendor as a reference, the contract manager may give the impression of favoritism or bias towards that vendor when making decisions related to contracting or procurement.
A government agency's mission statement should include its major functions and goals. A mission statement is a concise statement that articulates the purpose and core objectives of an organization. In the case of a government agency, the mission statement should clearly communicate its major functions and the overarching goals it aims to achieve.