eBay vs Mercadolibre

eBay's REST platform — Browse, Sell, and related APIs — requires an OAuth2 client-credentials or authorization-code token, confirmed live by a standard invalid_client error from its token endpoint, and is built for server-side integration rather than in-browser calls. New developer accounts get a free daily call allowance with no published paid tier, and higher volume comes from an approval process rather than a fee.

Mercado Libre exposes a large REST surface across its Latin American marketplace sites, covering listings, orders, ads, and shipping. Public reference data like site categories is reachable without a token, but anything scoped to a seller account requires an OAuth2 access token obtained via an authorization-code or client-credentials grant. The API itself carries no direct usage fee — Mercado Libre monetizes through marketplace and payment commissions instead.