# API Configuration
source: https://developer.mastercard.com/mastercard-processing-fraud/documentation/api-basics-section/configuration/index.md

The Mastercard Processing Fraud API enables a customized configuration for each issuer to align with specific requirements. The configuration includes, among others, definitions of special fields, available characters, and dictionaries. A part of the API configuration is also a list of `operationId` enabled for each issuer.
Note: If you try to execute the `operationId` that is disabled in your API configuration, you will receive a dedicated error. For more information about error messages, see [Error Codes](https://developer.mastercard.com/mastercard-processing-fraud/documentation/code-and-formats/index.md).