How would I enter nested parameters and mapped data?

I'm new to the Ready!API tool and I'm running into a few issues.  My two major issues are displayed in the example code below.

First, I'm having trouble entering nested parameters for the "markings" parameter in the tool. The standard string parameters are fairly straight forward, but I can't find any documentation on adding nested parameters.

Second, we employ a mapping strategy for a number of our calls. This particular call uses mapped data for "animal" and "origin". I'm not sure how I can set this up with the tool.  

Any help is greatly appriciated. 

{
"animal":{
"breed":"Angus",
"species":"Equine",
"otherImages": [4,5],
"headCount":1,
"color":"purple",
"name":"Animal 3",
"age":"young",
"gender":"male",
"markings": {
"otherMarkings":"testing1",
"headMarkings":"testing2",
},
"brandDescription": "a fancy description"
},
"origin":{
"lastName":"Fenix",
"name":"Marcus Fenix",
"type":"Person",
"firstName":"Marcus",
"cellPhone":"555-444-1234",
"ownerEmail":"marcus@funweek.com",
"mi":null,
}
}