Pricing is done on a per-operation basis. Each request you make to our API will count as 1 or multiple operations depending on the content submitted.
For Text Classification models as well as for Rule-based pattern-matching algorithms, we will count 1 operation up to 1000 characters and then an extra operation for each extra 1000 characters. So if you do a request with a text that is 1800 characters long, that will count as 2 operations.
Each time you perform a request to the API, the response field contains an operations key with details on the number of operations counted for this request.