Focus on lead times, inventory visibility, and picking throughput. Key metrics: order cycle time, pick accuracy, and cost per line. Verify WMS integrations (API/EDI), SLA terms for same-day/next-day options, and the provider's track record with returns and peak-season scaling.

Request historical transit-time matrices and carrier rosters. Evaluate road connectivity to major ports and interstate corridors, density of national and regional carriers, freight consolidation options, and published OTP (on-time pickup/delivery) statistics to model landed-cost impact.

Prioritize modern WMS with real-time inventory, automated sorting or conveyor systems for high SKU counts, temperature-controlled bays if needed, secure cross-dock space, and clear SOPs for value-added services like kitting, labeling, and returns processing.

Compare fixed vs variable fees, storage density charges, pick-and-pack rates, inbound receiving fees, and minimum monthlys. Model cost per order under target volumes and include transport to customer zones; request sample invoices and SLA penalties to reveal hidden costs.