# Helping a child compare a trade

Proposal, October 12, 2026. No trade evaluator or live price calls are enabled in this release.

The proposed view has two sides: “Giving” and “Getting.” Each side records exact printing, finish (normal, holo or reverse holo), language, quantity and the condition the family reports. Both sides must be identified before comparing them. HP and printed damage do not determine a card’s market price.

The app can deterministically show which saved decks lose needed copies, whether a trade removes an evolution step, what the incoming card could help with, duplicates, and favorited cards. These checks use the known collection and deck rules. They do not need an LLM.

Price comparison needs external data. The Pokémon TCG API documents TCGplayer and Cardmarket price fields and update dates: https://docs.pokemontcg.io/api-reference/cards/card-object/. Direct TCGplayer developer access is not currently offered to new applicants: https://docs.tcgplayer.com/docs/getting-started. This is a source option to investigate, not a promise of live coverage or a paid integration.

Use an explicit “Check prices” button. Send printing IDs or search text, not photos or personal information. Cache successful results for a short period, avoid retries on rate limits, and show source, currency, finish, and timestamp. Never sum USD with EUR. Missing, old, condition-mismatched or finish-mismatched data must remain unknown rather than becoming zero.

Only compare both totals when they use compatible source, currency, condition assumptions and freshness. Prefer a range to a single authoritative number. Show the arithmetic and deck impact separately. The family may knowingly accept a less valuable card because it completes a deck or is a favorite.

A photo cannot certify authenticity, accurately grade condition, or guarantee what someone will pay. A helpful result says what needs checking, rather than declaring “safe” or “fair.” Include a pause-and-ask-a-grown-up step for uncertain or high-value trades. No trade updates owned cards until a parent explicitly confirms the completed exchange.

Next decision: prove price coverage for the exact printings families scan, including older cards and variants, before choosing a provider or introducing any cost.