Mercado Pago API reference - all the information you need to develop your integrations.
MercadoPago API is a free Finance API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.
Introducción
Details from mercadopago.com.br.

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The MercadoPago API is provided by Mercado Pago Developers (mercadopago.com.br). Introducción
Yes. The MercadoPago API is listed in the Finance category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
Yes. The MercadoPago API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the MercadoPago API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The MercadoPago API is served over HTTPS, so it's safe to use in production.