Prioritize measurable KPIs: order accuracy and on-time fulfilment rates, inventory visibility and reconciliation cadence, throughput capacity during peak windows, SLA penalties, and ability to integrate via API/EDI with your ERP or marketplace platforms. Also validate physical capabilities like racking, cold chain, and cross-docking lanes.

Evaluate the 3PL's carrier roster and transit lanes, rail and highway connections, airport cargo handling, and documented experience with cross-border customs and documentation. Confirm consolidated freight options, transit-time maps to primary destinations, and contingency routing for seasonal disruptions.

Model fixed and variable costs: per-pallet and per-sku storage, picking/packing labor rates, inbound receiving fees, minimum monthly charges, order handling tiers, returns processing, equipment surcharges, and fuel or regional access fees. Include projected shrink, demurrage, and seasonal volume impacts to estimate true landed cost.

Run integration pilots for WMS/API connectivity, request sample reports and real-time stock feeds, perform a physical audit or cycle-count trial, confirm access to event-level transaction logs, and negotiate phased SLAs with benchmarks tied to go-live and scaling milestones. Ensure support for exceptions, chargebacks, and regular operational reviews.