HTTP POST To API for query source - Passing Parameters to API using Power Automate POST URL

Greetings, I have an API Call that works fine in Postman when specifiying parameters, however, when I try to post to the same URL, passing the parameters in PQ, I receive a 400 Bad Request error. I'm inclined to believe it is the syntax of my PQ, however, I am stuck as to where / what it may be. 

Sample code below: 

let
    
    PostURL = "https://prod-59.westus.logic.azure.com:443/workflows/281583e6ee6b45d6705dfaa8531/triggers/manual/paths/invoke?api-version=2016-06-01&sp=%2Ftriggers%2Fmanual%2Frun&sv=1.0&sig=W1O8t6yfYjcXLPsmKZdmE7PsvxFWtZUjz2miFY"
    , AccessKey2 = "aaaaa-bbbbb-ccccc-ddddd-eeeee"
    , TenantURL2= "https://yourtenant.sharepoint.com"

    , Source = Json.Document(
                    Web.Contents(
                        PostURL    
                        , [Headers=[#"content-type"="application/json"]
                        , Content = 
                            Json.FromValue(
                                {[AccessKey=AccessKey2,TenantURL=TenantURL2]}
                                )
                           ]
                                )
                              )   

    in Source

The above code does not work in PQ, however, the below Postman code snippet for http POST works okay. 

I'm pretty sure it is how I'm passing the Content Parameters, but I'm not sure where my error is. 

Postman code:

POST /workflows/281583e6ee6b4b6705dfaa8531/triggers/manual/paths/invoke?api-version=2016-06-01&sp=%2Ftriggers%2Fmanual%2Frun&sv=1.0&sig=W1O8t6yfYfgXLPsmKZdmE7PsvxFWtZUjz2miFY HTTP/1.1
Host: prod-59.westus.logic.azure.com:443
Content-Type: application/json
Content-Length: 112

{
"AccessKey": "aaaaa-bbbbb-ccccc-ddddd-eeeee",
"TenantURL": "https://yourtenant.sharepoint.com"

}