Prioritize a partner that provides a robust WMS with real-time inventory, proven pick‑pack accuracy, SLA-backed lead times, and flexible labor for peaks. Also evaluate returns processing, kitting and light assembly, packaging options, and seamless API integrations for order and shipment orchestration.

Review the 3PL's carrier panel and transit time matrices for key lanes, parcel and LTL agreements, and hub proximity. Confirm multimodal options, scheduled cutoffs, and performance metrics (on‑time pickup/delivery). Verify experience with cross-border documentation if you operate international lanes.

Negotiate transparent unit rates for receiving, storage tiers, pick/pack, and value‑added services. Secure bandwidth commitments, volume discounts, clear chargeback rules for deductions, and indexed rate review clauses tied to measurable KPIs to avoid hidden fees and manage total landed cost.

Ensure the 3PL supports secure API or EDI connections for order, inventory and shipment events; offers real-time inventory visibility and reporting; and can integrate with your OMS, ERP, and carrier management systems. Confirm SLA for onboarding, testing, and ongoing support.

Evaluate the partner's available capacity, contingency plans for labor or power outages, disaster recovery procedures, insurance coverages, and ability to add temporary shifts or space. Review historical performance during peaks and request references for similar-scale migrations.