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E-commerce

Inventory Replenishment Planning

AIBarsMITSkill language: English
License verifiedNo scriptsLow risk
DemoReal run · claude-sonnet-5-5 · October 2026
I run a small store with three products and need a reorder plan. Supplier lead time is about 21 days by sea (the last four shipments took 19, 21, 24 and 27 days). I want roughly a 95% service level on the best seller. Weekly units sold over the last 8 weeks: Product A (best seller, cost 9.00): 140, 155, 128, 162, 149, 135, 170, 151. On hand 420, nothing on order. Minimum order 500. Product B (cost 15.00): 22, 18, 25, 20, 19, 27, 21, 23. On hand 310, 100 arriving in 10 days. Minimum order 200. Product C (cost 6.00): 3, 0, 2, 1, 0, 2, 1, 1. On hand 540, nothing on order. No sales of the dark blue variant (120 units) in 100 days. Cash available for the next order is 4,500. What should I order now?
Skill: inventory-replenishment-planning

Reorder plan: order 500 units of Product A now and nothing else

That is the supplier minimum, and it costs 4,500, which uses all your cash. A is already below its reorder point. B and C have far more stock than they need.

Assumptions

  • Lead time: I used the mean of your last four shipments, 22.75 days, not the 21 days quoted. The standard deviation is 3.5 days, and it is the biggest risk in the plan.
  • Service level: 95% for A (z = 1.65).
  • Demand: weekly sales from the last 8 weeks, converted to daily. Eight weeks is a short history, and I assumed no seasonality or promotions.
  • ABC ranking: I used cost value because you didn't give selling prices.

ABC and dead stock

SKU Avg/week Weekly cost value Class
A 148.75 ~1,339 A (~80%)
B 21.9 ~328 B (~20%)
C 1.25 ~8 C (<1%)
  • C dark blue: 120 units (720 at cost) with no sales in 100 days is dead stock. Clear it with a discount or a bundle, and don't reorder it.
  • C overall: 540 units is about 430 weeks of supply, or roughly 8 years. Stop buying C and treat the rest as slow clearance.

Per-SKU plan

Product A (order now)

  • Daily demand is 21.25 units, with a daily standard deviation of 5.28.
  • Demand over the lead time is 21.25 × 22.75 ≈ 483 units.
  • Safety stock is 1.65 × √(22.75 × 5.28² + 21.25² × 3.5²) ≈ 130 units.
  • Reorder point is 483 + 130 ≈ 613 units. You have 420, so you are below it.
  • Cover is 420 / 21.25 ≈ 20 days, which is less than the 22.75-day lead time.
  • A order placed today is expected to arrive after you run out, by about 3 days, or roughly 60 units of lost sales. Even a perfect order can't prevent that.
  • The ideal order covers the lead time plus a 30-day review period. That is 21.25 × 52.75 + 130 − 420 ≈ 830 units (about 7,470).
  • Your cash covers only 500 units. That gives about 23 days of cover once it arrives, so you will need to reorder again very soon.

Product B (don't order)

  • Daily demand is 3.1 units. Stock is 310 on hand plus 100 arriving, 410 in total, which is about 131 days of cover.
  • Its reorder point is about 87 units, so you won't be near it for months.
  • The 200-unit minimum order would only add to the overstock.

Product C (don't order)

  • See the dead-stock notes above.

Cash

  • The 4,500 goes entirely to A.
  • To fund the 330-unit gap (about 2,970), free cash from slow stock. Stock tied up is B at 4,650 (310 units at 15) and C at 3,240 (540 at 6).
  • Clearing the dark blue C (720) and part of C's remaining stock is the easiest cash to free. Hold off on B's 100 incoming units only if the supplier allows it.

Risks

  • Lead-time variability: at the 27-day worst case, demand over the lead time is about 574 units, so you'd stock out about 7 days before arrival. Ask the supplier about splitting the order, or air-freighting a small top-up (about 60–100 units) to bridge the gap.
  • Short history: 8 weeks is a weak basis, and an upswing or a promotion would raise the numbers.
  • Supplier terms: confirm the minimum order, payment terms and any freight costs. Freight isn't in the 4,500.

What to measure next

  • Actual lead time for each shipment.
  • Stockout days for A.
  • Weekly forecast error.
  • Sell-through of the C clearance.
  • Reorder A again as soon as cash allows. Don't wait for the 500 units to arrive.

If you give me selling prices and a freight cost, I can redo the ABC ranking on margin and check whether the 4,500 still buys 500 units.

Real run in an isolated folder with only this skill installed. Only the Skill and Read tools were enabled, so no command was run and no file was written. The store and all numbers are invented and the model had no access to a real store. The lead-time statistics, safety stock and reorder point were recomputed by hand afterwards and matched.

What it does

Plans replenishment per SKU (each variant separately) from sales history and supplier lead times. It classifies items by ABC, marks dead stock, and computes average demand (excluding out-of-stock days), safety stock with the service level you choose, the reorder point, days of cover and an order quantity, including the effect of lead-time variability, which is often larger than demand variability. It then adjusts for trend, season, promotions, new products, long sea freight and cash, and lists symptoms with likely causes (keeps running out, dead stock, tight cash).

Output

Assumptions with sources, an ABC table with the dead-stock list and suggested actions, a per-SKU plan with what to order now, the weak estimates and what would change the plan, and what to measure next. A worked example with numbers is built into the skill.

Good for

A reorder plan for a small store, finding why products keep running out, and clearing slow stock.

Notes & risks

Low risk: pure instructions with no scripts, no network access and no file writes. A plan is not a forecast or a promise: demand and delivery are uncertain, and the skill states the service level it is aiming for. Check supplier minimums, freight, customs and storage rules with the supplier or carrier; they differ by country and change. It cannot see your inventory system and uses only the numbers you give. Original skill by AIBars (MIT). Tried once on an invented three-product store; its statistics were checked by hand afterwards.