WSO2 create API for SCEP server HTTP GET POST

Question

I have a SCEP endpoint (Simple Certificate Enrollment Protocol) which is using simple HTTP GET and POST with parameters, for example:

http://localhost/scepserver/pkiclient.exe?operation=GetCACaps&message=CA

I am trying to implement this API in WSO2 Api Manager with endpoint to my SCEP server. I was trying to do it using "Design a New REST API" but it is not working and I do not want to use JSON in message payload.

How should I define API for SCEP, with example to call endpoint with query parameters?

EDIT:

Trying through curl:

curl -X GET 'http://10.30.9.145:8280/devscep/1/pkiclient.exe?operation=GetCACaps&message=CA' -v

Result:

* Hostname was NOT found in DNS cache
*   Trying 10.30.9.145...
* Connected to 10.30.9.145 (10.30.9.145) port 8280 (#0)
> GET /devscep/1/pkiclient.exe?operation=GetCACaps&message=CA HTTP/1.1
> User-Agent: curl/7.38.0
> Host: 10.30.9.145:8280
> Accept: */*
>
< HTTP/1.1 401 Unauthorized
< activityID: 22588072245075117976472
< WWW-Authenticate: realm="WSO2 API Manager"
< Content-Type: application/soap+xml; charset=UTF-8
< Date: Fri, 14 Jul 2017 13:02:16 GMT
< Transfer-Encoding: chunked
<
* Connection #0 to host 10.30.9.145 left intact
<?xml version='1.0' encoding='UTF-8'?><soapenv:Envelope xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope"><soapenv:Body/></soapenv:Envelope>

Answer 1

In the resources section of the design page, you can define expected query parameters for each resource.

https://docs.wso2.com/display/AM210/Key+Concepts#KeyConcepts-APIresources