You can start using the Sintra API straight away. You don't even need an API key. Just start hitting the endpoints and you will get pricing data back. To view the available endpoints see the API docs.
Requests made without an API key will be subjected to lower rate limits.
We are currently working on our Pro plan which will be more suitable for apps that have a larger user base. Once the Pro plan is ready you will be able to choose it from the pricing section on the homepage.