The goal is to create a codeunit to manage POS terminal APIs efficiently within an extension.

1. Access Property: Setting Access = Internal is the best practice for codeunits that provide logic meant to be used only within the current extension. It prevents other extensions from calling these procedures, maintaining encapsulation. Public would expose it globally, which is often unnecessary for internal API management.
2. Procedure Declaration: The OnRun trigger calls readAPI(); without passing any arguments. Therefore, the procedure must be defined as procedure readAPI() to match the signature of the call. The var prefix is used for parameter definitions, not the procedure name itself, and providing an integer parameter would cause a compilation error due to a signature mismatch.

Microsoft Learn: Codeunit Object - Documentation on properties and triggers. Access Property in AL

Microsoft Learn: AL Simple Statements - Explaining procedure calls and parameter matching. Procedures in AL

Microsoft Dynamics 365 Business Central Development: Best Practices for Extension Development - Guidance on encapsulation and access modifiers.