Weekly ShipStation shipping performance digest

Every Monday at 9am in my local timezone, run a cron workflow that generates a written weekly shipping performance digest for the ops team and posts it as a single Slack message using the Slack Bot integration (so the message comes from a shared bot, not a personal account).

Pull last week's data from ShipStation. Use List Labels with a date range filter covering the previous Monday through Sunday. Also call List Carriers once so you can map raw carrier_id values to friendly carrier names (UPS, USPS, FedEx, DHL, etc.) in the digest. ShipStation money fields like shipment_cost are returned as objects shaped { amount, currency }, so unwrap amount before summing or averaging. Paginate List Labels until you have every label in the window.

Aggregate the labels by carrier. For each carrier, compute: total labels purchased, total spend (sum of shipment_cost.amount), and average cost per shipment. Then pull the prior week with the same logic and compute week-over-week percentage change in total spend, average cost per shipment, and label volume for each carrier.

In the digest, also call out: (1) the single most expensive shipment of the week (carrier, service, cost, destination if available); (2) the carrier with the best (lowest) average cost per shipment that week; and (3) any carrier where average cost per shipment spiked sharply versus the prior week, or where volume dropped sharply. Use roughly a 20% change as the default threshold but apply judgment based on volume so we don't flag noise from a carrier that only had two shipments.

Format the output as a readable Slack message using Slack mrkdwn (single asterisks for bold, no double asterisks, plain bullet lists). Structure it as: a short headline with the date range and total weekly spend, then a per-carrier breakdown table-style block, then the callouts at the bottom. Keep it scannable in under one screen height. Post to #shipping-ops by default and let me change the channel during setup.

If the window had zero labels, still post the digest with a one-line note that there was no shipping activity last week instead of sending an empty report.