Agricultural data markets are becoming integral to precision farming as data generated by sensors, machinery, remote-sensing systems, farm-management platforms, advisory services, supply chains, and public information infrastructures acquire operational and economic value. However, the expansion of data exchange creates policy challenges that cannot be assessed through innovation, productivity, or monetization potential alone. This article develops an original policy framework that connects agricultural data-market boundaries, actors, data flows, ownership claims, access arrangements, effective control, farmer participation, privacy, competition, platform power, interoperability, fair exchange, accountability, and implementation safeguards. The framework distinguishes data ownership from access, control, portability, consent, and practical farmer agency. It also treats privacy protection as one component of a wider governance architecture that must address platform dependency, market concentration, switching costs, asymmetric information, bargaining-power imbalances, data-intermediary influence, and unclear accountability. Interoperability is conceptualized as a combination of technical, semantic, organizational, and governance conditions rather than as a sufficient guarantee of fair exchange. The framework further identifies policy gaps involving ambiguous rights, fragmented portability, weak consent, opaque value capture, deficient dispute pathways, and limited monitoring capacity. Its principal contribution is a structured policy-analysis model that links risk identification to context-sensitive safeguards, stakeholder feedback, monitoring, and framework updating. The framework supports policy-oriented analysis but does not independently establish legal compliance, guarantee farmer protection, certify market fairness, or demonstrate implementation readiness.