The Odoo API is free to use for all Customers on the Custom Plan.

See odoo.com/pricing for details.

We have limits on acceptable use - throttled calls are typically acceptable for unsustained usage at a rate of 1 call/second, with no parallel calls.

See odoo.com/acceptable-use for details.

Hi,

Maximum request size: The amount of data you can transmit in a single request for many APIs is limited. Usually, this is expressed in bytes or gigabytes. If you send more than this, you might get an error or the request might just be disregarded.  Maximum number of requests: APIs may also place restrictions on how many you can send in a particular amount of time. Requests per minute or requests per hour are frequently used to quantify this. If you go over this restriction, you might get an error or have your account briefly suspended.  Cost per request: While some APIs are free to use, there may be others that charge a one-time cost or a monthly subscription charge.Depending on the API and the number of requests you make, the cost per request can differ significantly. 

Regards