SCP API - Adding Request

SCP API - Adding Request

I am an experienced SDP user who is configuring a support center plus enterprise edition install for another business unit.  In SDP I was able to add requests using a URL such as this:

https://my.server.com/sdpapi/request/?OPERATION_NAME=ADD_REQUEST&TECHNICIAN_KEY=00000000-0000-0000-0000-000000000000&INPUT_DATA=<Operation><Details><requester>Bob Barker</requester><subject>The Price is Right</subject><description>blah</description><category>category</category><subcategory>subcategory</subcategory><item>item</item><priority>P3</priority><site>Site</site><group>TestTeam</group><department>IT</department><SLA>SLA</SLA></Details></Operation>

When trying to translate this same functionality over to SCP I used this URL:

https://my.server.com/api/xml/addRequest?apikey=00000000-0000-0000-0000-000000000000&<email>email@email.com</email><subject>API</subject><description>description</description>

However it throws error "4002 - HTTP Post Request is required to perform this operation"

What am I doing wrong?