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Shopping & Errands

Hunt high-value Pokémon cards on eBay overnight

An engineer built a Codex agent that browses eBay listings, extracts PSA certificate numbers and cross-references known prices while he sleeps.

Done withCodex

What they did
Alessio Finelli gave the Codex agent a sparse skill file with rules on target cards, batch size of 5, and grading companies. The agent browses eBay listings on its own, extracts PSA certificate numbers, cross-references known prices, and flags underpriced high-value cards. He steps in only to review flags for his physical shop.
How it went
It works as his power buyer, surfacing underpriced cards before others see them.
Worth knowing
Limit batches to 5 listings to avoid eBay bans; run on a cloud VPS.

Try it yourself with Codex

Write and run an agent that browses [marketplace, e.g. eBay] listings for [item type, e.g. graded Pokémon cards] under [max price], extracts each listing's [certificate or serial number], and compares it to prices in [price source or file]. Save listings that look underpriced by at least [percent]% to a file called [output file] with the link, price, and reference price. Stop after running it once on [number] listings and show me the results and how to schedule it overnight. Don't buy, bid, or message any sellers.

Read the original ↗

Source: X · Jul 18, 2026

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