There is no Terapeak API, and here is what to use

The short answer

eBay does not publish a Terapeak API. Developer support has said so directly on eBay's own forums: the tool is available through Seller Hub and the Research tab, and not as an API. If you are searching for Terapeak API documentation, that is why you cannot find any.

There have been two near misses. A Terapeak Beta API appeared in eBay's 2021 Connect material, open to a limited set of partners behind a waitlist, and it never became generally available. An older Insight API did exist and was withdrawn from public access. Neither is something you can sign up for today.

What eBay points you to instead

eBay staff redirect these questions to the Marketplace Insights API, which does return sold items by keyword, GTIN, category and product. The catch is in the first line of its own documentation: you have to apply for access, and in practice most teams are declined or left waiting. It is part of the Buy API family rather than anything Terapeak branded. If you have been granted it, use it. If you are reading this, you probably have not.

⚠ One piece of advice that circulates on those forum threads is wrong. The Trading API's GetSellerTransactions call does not give you market wide sold prices. It covers your own transactions, which is a different question entirely.

What we are, and what we are not

We are not eBay and we are not Terapeak, and we are not affiliated with either. What we do is return completed eBay sales as JSON over an ordinary HTTP API, with no application process, no developer account and no approval step. A free key needs no card.

The reason it is worth comparing to Terapeak at all is depth. eBay's public sold page shows roughly 90 days, which is the ceiling for nearly every third party sold data API because that is the surface they all read. We page through up to 1,095 days per search, which is the same order of history the Research tab shows you by hand. See the price history API.

curl -G https://api.compsapi.com/v1/sold \
  -H "Authorization: Bearer YOUR_KEY" \
  --data-urlencode "q=charizard psa 10" \
  --data-urlencode "days=1095" \
  --data-urlencode "best_offer=1"

The one thing even the Research tab will not tell you

On a sale that closed through an accepted Best Offer, eBay's public sold page shows the asking price with a strikethrough and never the amount paid. Across 5,859 matched sales we found the public figure read high 99.0% of the time, by a median of 14.9%. We return the settled amount, flagged per row. Method is in the study, and the field is on every plan.

If you were going to build it yourself

People usually arrive at this page after trying to automate the Research tab. It is worth knowing what that costs before you start: it is login walled, so you are maintaining sessions and accounts rather than just parsing a page, and that becomes an ongoing operational job rather than a one off script. That is the work we do so you do not have to.

If you want the migration shaped as a swap rather than an explanation, the Terapeak alternative page is the one to read, and the Marketplace Insights page covers that route.