Scan eBay for underpriced Pokémon cards overnight
An engineer used Codex to watch eBay listings, pull PSA certificate numbers, and compare them with known prices while they slept.
- What they did
- Alessio Finelli gave Codex a short skill file that set the target card types, a batch limit of five, and the grading services to watch. The agent then browsed eBay on its own, extracted PSA certificate numbers, checked them against known prices, and marked cards that looked too cheap.
- How it went
- It now acts as a buying assistant for his physical shop, surfacing bargains before other shoppers notice them. He only steps in to review the flagged cards, and the setup is kept in small batches to avoid eBay bans.
- Tips
- Keep the batch size small and run it on a cloud VPS. Have the agent stop and ask before any purchase, bid, or message goes out.
Try it yourself with Codex
Help me monitor [marketplace] for [item type] while I’m away. Use these rules: [target card or item types], [batch size], [grading companies or other filters]. For each listing, open the page, extract the [certificate number / serial number / identifier], compare it with [price source], and flag anything that looks underpriced by at least [percent]%. Save the matches to [output file] with the link, listing price, and reference price. After you finish the first pass, pause and show me the flagged items for approval before doing anything irreversible like buying, bidding, messaging sellers, submitting forms, or deleting anything. Do not take those actions unless I explicitly approve them.
Fill in the [brackets]. Agents can make mistakes, so review anything before it is sent, paid or deleted.
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