Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add zincio/skills --skill ebay-checkoutgit clone --depth 1 https://github.com/zincio/skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/zincio/skills/ebay-checkout)<a href="https://agentmods.dev/skills/zincio/skills/ebay-checkout"><img src="https://agentmods.dev/badge/skills/zincio/skills/ebay-checkout/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/zincio/skills/ebay-checkout"><img src="https://agentmods.dev/badge/skills/zincio/skills/ebay-checkout.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00127 | $0.03702 |
| Opus 5 | $0.00063 | $0.01851 |
| Sonnet 5 | $0.00025 | $0.00740 |
| Haiku 4.5 | $0.00013 | $0.00370 |
Grade A, and why
ebay-checkout scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 10d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
curl "https://api.zinc.com/search?q=cast+iron+skillet" \ This is a copy
92% identical to 1800flowers-checkout — 24 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 237 lines — stays where its author put it; the contents beside it link to each section on GitHub.
eBay Checkout
Buy, track, and return products from eBay (ebay.com) through the Zinc API (https://api.zinc.com). US orders.
Powered by Zinc Universal Checkout. The same API buys from eBay and 50+ other US retailers (Amazon, Walmart, Target, Best Buy, eBay, and more). To order across multiple retailers from one skill, install the
universal-checkoutskill (npx skills add zincio/skills --skill universal-checkout). Live retailer list:GET https://api.zinc.com/retailers.
Quick Start
Which auth method should I use?
ZINC_API_KEYenv var is set → UsePOST /orderswith Bearer token auth. This is the standard flow for pre-registered users.- MPP — no account needed → Use the
/agent/*endpoints and pay per request with a Stripe card (via Stripe Link — no crypto), Tempo stablecoins, or x402 (USDC on Base).POST /agent/ordersto buy;/agent/searchto discover ($0.01 per data call).GET /retailersis free. - Neither is set → Ask the user to either sign up at app.zinc.com for an API key, or set up an MPP payment method. Try it without code at agent.zinc.com.
All amounts are in US cents (e.g. 5000 = $50.00).
Authentication
API Key Auth
Authorization: Bearer $ZINC_API_KEY
MPP Auth (Machine Payments Protocol)
MPP is an open standard for HTTP 402 machine-to-machine payments (spec: mpp.dev) — no API key needed upfront:
- Send the request (e.g.
POST /agent/orders) with noAuthorizationheader → HTTP402 Payment Required. The challenge advertises every available rail: MPP methods as oneWWW-Authenticate: Payment …header each (method="stripe",method="tempo"), and x402 as aPAYMENT-REQUIREDheader (USDC on Base). - Pick the rail your client supports and pay, then retry: MPP methods resubmit with
Authorization: Payment <credential>; x402 clients resubmit with aPAYMENT-SIGNATUREheader. Client libraries handle this loop automatically. - For orders, save the
X-Api-Keyresponse header — a Bearer token scoped to that order, forGET /orders/{id}.
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 10d ago First seen · 237 lines · 127 tokens per session scan A cbc0cde5fd1b
ebay-checkout is a skill published in the GitHub repository zincio/skills (7 stars, last pushed 8d ago), licensed MIT. It adds 127 tokens to every session and 3,702 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). It is 92% identical to 1800flowers-checkout, differing in 24 lines, and is treated as a copy.
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