GET request not supported in custom API in Business Central. "BadRequest_MethodNotAllowed"

I try to call a method in a custom API in a code unit in Ms Dynamics 365 Business Central. I tried everything to make it a simple GET method, but I keep receiving "BadRequest_MethodNotAllowed" in Postman.

The complete response:

{"error": {"code": "BadRequest_MethodNotAllowed","message": "'GET' requests on unbound actions are not allowed."    }}

When I call the method with a POST request (in Postman), it works as expected.To me it seems absurd the caller of my API need to use POST when het wants to GET some data from my API. This is of course also against official guide lines and conventions.Am I missing something? Please some advice. Thank you.