Prioritize total landed cost (storage + handling + transport), service-level agreements (order accuracy, cut-off times), carrier connectivity, and the 3PL’s technology (WMS/EDI/API). Assess physical infrastructure (dock count, racking height, yard capacity), seasonal labor plans, and reporting transparency to ensure alignment with demand patterns.

Request facility tours or virtual walkthroughs, examine SKU slotting strategies, inspect dock and yard capacity, and review historical throughput metrics. Verify WMS capabilities, integration points, real-time inventory visibility, and contingency plans for peak seasons or carrier disruptions.

Key cost drivers include hourly/daily storage rates, pick-and-pack fees, inbound/outbound handling, value-added service charges (kitting/labeling), and transportation accessorials. Benchmark using per-SKU activity models, landed cost scenarios, and by comparing service tiers for accuracy and transit time trade-offs.

Look for real-time WMS APIs or robust EDI, daily inventory reconciliation, configurable order routing rules, and performance dashboards for KPIs (OTIF, pick accuracy, lead time). Ensure the provider supports SKU-level reporting, batch/lot tracking if required, and has clear SLAs for data exchange and issue resolution.