Invoke rest api not returing json

Making a request to the api in json for json returns XML.

Here is the request out bound request

OST https://172.24.251.158:17778/SolarWinds/InformationService/v3/Json/Invoke/Orion.Discovery/CreateCorePluginConfiguration

Accept: */*

Authorization: Basic xxxxxxxxx( not shown )

Content-Length: 371

Content-Type: application/json

[{"WmiRetriesCount":0,"Credentials":[{"CredentialID":78,"Order":"1"},{"Order":"2","CredentialID":77},{"CredentialID":85,"Order":"3"},{"CredentialID":82,"Order":"4"},{"CredentialID":84,"Order":"5"},{"CredentialID":92,"Order":"6"},{"Order":"7","CredentialID":3},{"CredentialID":73,"Order":"8"}],"BulkList":[{"Address":"165.237.101.81"}],"WmiRetryIntervalMiliseconds":1000}]

Here is the response from the server: ( it is not returning json)

HTTP/1.1 200 OK

Date: Fri, 11 May 2018 22:07:52 GMT

Server: Microsoft-HTTPAPI/2.0

Content-Length: 2686

Content-Type: application/json

"<?xml version=\"1.0\" encoding=\"utf-16\"?><PluginItems><knownTypes><ArrayOfstring xmlns:i=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns=\"http://schemas.microsoft.com/2003/10/Serialization/Arrays\"><string>SolarWinds.Orion.Core.Models.Discovery.CoreDiscoveryPluginConfiguration,SolarWinds.Orion.Core.Models</string></ArrayOfstring></knownTypes><pluginItem><ArrayOfDiscoveryPluginConfigurationBase xmlns:i=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns=\"http://schemas.datacontract.org/2004/07/SolarWinds.Orion.Core.Models.Discovery\"><DiscoveryPluginConfigurationBase xmlns:d2p1=\"http://schemas.solarwinds.com/2008/Orion\" i:type=\"d2p1:CoreDiscoveryPluginConfiguration\"><d2p1:ActiveDirectoryList /><d2p1:AddressRange /><d2p1:AgentsAddresses xmlns:d3p1=\"http://schemas.microsoft.com/2003/10/Serialization/Arrays\" /><d2p1:AutoImportVolumeTypes xmlns:d3p1=\"http://schemas.datacontract.org/2004/07/SolarWinds.Common.Snmp\" i:nil=\"true\" /><d2p1:BulkList xmlns:d3p1=\"http://schemas.microsoft.com/2003/10/Serialization/Arrays\"><d3p1:string>165.237.101.81</d3p1:string></d2p1:BulkList><d2p1:Credentials><d2p1:credentials><knownTypes><ArrayOfstring xmlns:i=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns=\"http://schemas.microsoft.com/2003/10/Serialization/Arrays\" /></knownTypes><pluginItem><d2p1:ArrayOfCredential xmlns:i=\"http://www.w3.org/2001/XMLSchema-instance\" /></pluginItem></d2p1:credentials></d2p1:Credentials><d2p1:DiscoverAgentNodes>false</d2p1:DiscoverAgentNodes><d2p1:PreferredPollingMethod>SNMP</d2p1:PreferredPollingMethod><d2p1:SharedCredentials xmlns:d3p1=\"http://schemas.microsoft.com/2003/10/Serialization/Arrays\"><d3p1:KeyValueOfintint><d3p1:Key>1</d3p1:Key><d3p1:Value>78</d3p1:Value></d3p1:KeyValueOfintint><d3p1:KeyValueOfintint><d3p1:Key>2</d3p1:Key><d3p1:Value>77</d3p1:Value></d3p1:KeyValueOfintint><d3p1:KeyValueOfintint><d3p1:Key>3</d3p1:Key><d3p1:Value>85</d3p1:Value></d3p1:KeyValueOfintint><d3p1:KeyValueOfintint><d3p1:Key>4</d3p1:Key><d3p1:Value>82</d3p1:Value></d3p1:KeyValueOfintint><d3p1:KeyValueOfintint><d3p1:Key>5</d3p1:Key><d3p1:Value>84</d3p1:Value></d3p1:KeyValueOfintint><d3p1:KeyValueOfintint><d3p1:Key>6</d3p1:Key><d3p1:Value>92</d3p1:Value></d3p1:KeyValueOfintint><d3p1:KeyValueOfintint><d3p1:Key>7</d3p1:Key><d3p1:Value>3</d3p1:Value></d3p1:KeyValueOfintint><d3p1:KeyValueOfintint><d3p1:Key>8</d3p1:Key><d3p1:Value>73</d3p1:Value></d3p1:KeyValueOfintint></d2p1:SharedCredentials><d2p1:SubnetList /><d2p1:WMICredentials /><d2p1:WmiRetries>0</d2p1:WmiRetries><d2p1:WmiRetryInterval>PT1S</d2p1:WmiRetryInterval></DiscoveryPluginConfigurationBase></ArrayOfDiscoveryPluginConfigurationBase></pluginItem></PluginItems>"