Safe Seller Toolkit

Overview

Peer-to-peer marketplaces move enormous volumes of secondhand goods — and concentrate fraud. The Internet Crime Complaint Center logged billions in losses from non-delivery/non-payment fraud alone; marketplace scams (overpayment, Google-Voice code hijack, fake shipping labels, off-platform payment) are the everyday layer beneath that. Casual sellers list a phone, get four messages in an hour, and three are scripts written by professionals.

This skill gives the seller four instruments:

1. price — 16 category depreciation curves × 5 condition grades → list/expect/floor price band plus market-behavior notes.
2. message — inbound buyer text scored against 9 scam families (40+ trigger phrases) → 0-100 scam likelihood, BLOCK/PROCEED verdict, and a safe one-line reply.
3. meetup — value-scaled in-person safety checklist (police exchange zones, IMEI verification, bank-lobby protocol for high-value deals) plus hard no-go conditions.
4. labels — shipping service comparison, packaging rules, proof-pack photography, and the do-not-ship fraud list.

Pure stdlib, offline, logs nothing.

When to Use

• "Someone offered to pay full price without questions — is this a scam?"
• "How much should I list my 2-year-old iPhone / laptop / couch for?"
• "A buyer wants me to ship to their agent / send a code / take Zelle"
• Preparing a first in-person sale (meetup checklist)
• "Got an offer on Marketplace, feels off, check this message"
• Selling high-value items ($300+ phones, bikes, cameras, laptops)

Don't use for: business/inventory-scale selling (different economics), real-estate or vehicle-title transfers (legal process beyond scope), or as a substitute for platform-specific dispute processes once fraud already happened (report + chargeback paths differ by platform).

How It Works — Numbered Steps

1. Price the item: python3 scripts/seller_toolkit.py price --category iphone --condition good --original 799 --age-years 2 → list $447 / expect $388 / floor $330. Cross-check against sold listings for the exact model; the band is a starting anchor, not gospel.
2. List with the safe-reply ready. When messages arrive, triage each: python3 scripts/seller_toolkit.py message --text "I'll send a 6-digit code..." → per-signal breakdown, score, verdict (BLOCK / PROCEED WITH RULES / LIKELY FINE), and a safe reply line.
3. Arrange the meetup with the checklist: python3 scripts/seller_toolkit.py meetup --item "iPhone 13" --price 350 High-value deals escalate automatically (bank lobby, IMEI/serial checks).
4. If shipping instead: python3 scripts/seller_toolkit.py labels --weight-lb 3.2 --dimensions 12x9x4 --value 350 Ship only after payment reads COMPLETED, never 'pending'.
5. Walk away on any no-go condition. The sale you lose to a scammer costs more than the sale you decline from a weird-but-honest buyer.

The 9 Scam Families (message triage)

Score ≥40 → BLOCK. 15-39 → PROCEED WITH RULES (one terms reply, second offense = block). Under 15 → normal caution.

Common Pitfalls

1. Sharing ANY verification code. The "buyer" is porting your number to Google Voice to run scams as you. Codes are never shared, ever.
2. Accepting 'pending' payments. Zelle/Venmo/payments can be reversed or fake-screenshotted. Cleared and completed, or cash counted in hand.
3. Refunding an overpayment. Their payment bounces; your refund is real.
4. Shipping on the buyer's label. Fake labels get your package stolen or delivered nowhere; you have no proof of delivery for disputes.
5. Meeting at home because it's heavy. Couch sellers get robbed. Meet in the driveway with a friend, or pay a mover — never alone inside.
6. Pricing from active listings. Active = unsold = overpriced. Search SOLD/completed listings and undercut the cheapest comparable.
7. Answering scam scripts with engagement. Every reply confirms your account is active and human. Block, don't debate.
8. Skipping the proof pack. Photograph the item powered on + serial before boxing. It's your only evidence in a 'item not as described' scam.

Example

Seller listing a 2-year-old iPhone 13, gets an instant message.

$ price --category iphone --condition good --original 799 --age-years 2
→ List $447 / expect $388 / floor $330 (retention 49%)

Buyer: "I'm out of town, my shipper will pick it up. I'll send a 6-digit
code to confirm, zelle you extra $50, text me asap."

$ message --text "<paste>"
→ [+40] code phishing  [+30] off-platform payment
  [+30] courier shipping  [+15] urgency
→ SCAM LIKELIHOOD 100/100 — VERDICT: BLOCK
  Safe reply: "Cash in person only. No codes, no shipping, no agents."

Second buyer: "Is the battery health above 85%? Can we meet at the
police station exchange zone tomorrow?"
→ 0 signals, LIKELY FINE → meetup checklist, station flag on.

References

• references/scam-field-guide.md — each scam family anatomy: the script, the psychology, the exact counter, and what to do if already hit.
• references/pricing-curves.md — the depreciation model, category table, condition multipliers, and local-market calibration method.