Query Org's Certificates in Apex using Metadata API

Question

I am unable to retrieve the Certificates of an org using the Financial Force Metadata API Apex Wrapper although I see the object in the Metadata API Documentation and can query it using the workbench.

When I call:

MetadataService.MetadataPort service = new MetadataService.MetadataPort();
service.SessionHeader = new MetadataService.SessionHeader_element();
service.SessionHeader.sessionId = UserInfo.getSessionId();  

MetadataService.ListMetadataQuery query = new MetadataService.ListMetadataQuery();
query.type_x = 'Certificate';

for(MetadataService.FileProperties prop : service.listMetadata(new List<MetadataService.ListMetadataQuery>{ query }, 25)) {
    System.debug(prop.fullName);
}

I get:

Line: 13524, Column: 1 System.CalloutException: Web service callout failed: WebService returned a SOAP Fault: INVALID_TYPE: Cannot use: Certificate in this version faultcode=sf:INVALID_TYPE faultactor=

I also tried "certs", "cert", "certificates" for query.type_x.

Note: this is breaking down my issues of Create Certificate/SSO Config in Apex using Metadata API into multiple questions as I didn't get any helpful feedback there.

Answer 1

I was able to query the Certificates using the Tooling API instead:

HttpRequest request = new HttpRequest();
request.setEndpoint(URL.getOrgDomainUrl().toExternalForm() + '/services/data/v46.0/tooling/query?q=Select+Id,DeveloperName+FROM+' +  type);
request.setMethod('GET');
request.setHeader('Authorization', 'OAuth ' + UserInfo.getSessionId());
request.setHeader('Content-Type', 'application/json');

ToolinApiResponse response = (ToolinApiResponse)
                                JSON.deserialize(new Http().send(request).getBody(), ToolinApiResponse.class);