F5 API - Unexpected Argument on /mgm/tm/ltm/policy

I took your request and only modified the referenced policy (changed to /Common/test for my lab) and it worked without issue, v13.1.0.3.

It's strange that it believes "policy": "/WebSeal/Test-Policy2" to be an unexpected argument, if it truly was unexpected it would fail in my lab too.

It's valid JSON too.

{  
   "name":"asm_auto_l7_policy__testserver-443",
   "partition":"/Common/Drafts/",
   "controls":[  
      "asm"
   ],
   "requires":[  
      "http"
   ],
   "status":"legacy",
   "strategy":"/Common/first-match",
   "rules":[  
      {  
         "name":"default",
         "fullPath":"default",
         "ordinal":1,
         "actions":[  
            {  
               "name":"1",
               "fullPath":"1",
               "asm":true,
               "code":0,
               "enable":true,
               "expirySecs":0,
               "length":0,
               "offset":0,
               "policy":"/WebSeal/Test-Policy2",
               "port":0,
               "request":true,
               "status":0,
               "timeout":0,
               "vlanId":0
            }
         ]
      }
   ]
}