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. Two read-only lookups work without a token: a category by ID, such as `/categories/MLA1051`, and `/sites/{site}/domain_discovery/search`. Everything else, including site lists, currencies, item listings and search, needs an OAuth2 access token from the authorization-code flow. The API itself carries no direct usage fee. Mercado Libre monetizes through marketplace and payment commissions instead.