What means a static response from an API and Sandbox? - api

Question

I am working for the first time with API-s. My first task at my job is to call an API, I am working with the Sandbox version of the API
I am trying to call the Sandbox this way and I should get a static response, but I am getting
"Error at message validation"
what means this and what exactly is a Sandbox and what is a static response?
procedure consentrequest(out transactionid1:transactionIdType);
var
Httprio2 : THTTPRio;
initiateConsentRequest1 : initiateConsentRequest;
initiateconsentrequestresponse1 : initiateconsentrequestresponse;
type2 :consenttype;
consent_init : consent2;
//AccountInfo_PT2 : AccountInfo_PT;
//transactionId1 : transactionIdType;
begin
initiateConsentRequest1 :=initiateConsentRequest.Create;
initiateconsentrequestresponse1 :=initiateconsentrequestresponse.Create;
consent_init :=consent2.Create;
HTTPRio2 :=THTTPRIO.Create(nil);
HTTPRio2.Url := 'https://sandbox.budapestbank.hu/OpenapiSandbox/v1.0.0';
consent_init.type_ :=type2;
consent_init.target := 'HU12345678901234567890123456';
consent_init.validityPeriod :=30;
initiateConsentRequest1.consent :=consent_init;
ShowMessage('Before PT');
initiateconsentrequestresponse1 :=(HTTPRio2 as AccountInfo_PT).initiateConsentRequest(initiateConsentRequest1);
ShowMessage('After PT');
transactionid1 := initiateconsentrequestresponse1.transactionId;
end;

Answer 1

A Sandbox is usually a non-production copy of the API, you might use different creds and get sample data responses. It's a safe practice space for developers.
The error about "message validation" makes me think that the API request you sent was somehow invalid, perhaps it is missing a parameter. Check the docs of the API you are calling and make sure you have the correct verb/endpoint and parameters. Also see if there is more information in the response itself.