Require measurable SLAs and KPIs: order accuracy (%), on-time shipment rate, average pick-to-ship time, inventory accuracy, receiving throughput, and returns processing time. Ask for historical reporting, chargeback terms for SLA misses, and visibility into root-cause analyses to ensure continuous improvement.

Evaluate a 3PL’s carrier connectivity and lane density: proximity to interstates/rail, integration with national parcel and regional LTL networks, and local final-mile partners. These factors determine transit windows, shipping cost bands, and the ability to consolidate shipments across channels.

Prioritize WMS with API connectivity, real-time inventory visibility, barcode scanning, scalable labor models, and automated sortation where needed. Also confirm support for kitting, returns processing, batch/pick optimization, and capacity flexibility for seasonal surges.

Build a cost model that includes receiving and putaway, storage (per pallet/cubic or per SKU), pick-and-pack fees, packing materials, outbound shipping accessorials, returns handling, kitting/setup fees, minimum monthly charges, and any integration or onboarding costs to determine true landed fulfillment cost.