Custom API with Json (Json contains Parent and Child records details)

Hello Everyone,

We are using custom API concept which is released by Microsoft recently,

https://docs.microsoft.com/en-us/powerapps/developer/data-platform/custom-api . The problem is, we have Json data as input parameter which contains Parent and Child record details. for example, here i have mentioned account (parent) and contact params. Number of Child records will be vary in each request.

{
"accountname":"Test account",
"accountnumber":"12345",
"description":"Test account created by user",
"city":"mumbai",
"country":"india",
"new_contact_account":[
{
"contactname":"abcd",
"contacttype":"phone",
"mobilenumber":"9087654321",
"email":"test1@gmail.com",
"comments":"Hello1",
"reference1":"",
"reference2":""
},
{
"contactname":"xyz",
"contacttype":"phone",
"mobilenumber":"9876543210",
"email":"test2@gmail.com",
"comments":"Hello2",
"reference1":"",
"reference2":""
}
]
}

Please let me know how to accept this Json in custom API input parameter and how to read child records one by one to process in plugin.

Please help me on this.

Thanks in advance.