REST API v3: How to edit an asset?

I need help forming my JSON for this. The reply message that I get back is simply "Internal Error" without any other identifying output to help track down the issue. I can update Location by itself just fine, but I cannot update the State with the current JSON parameters.

$id = "111111"
$input = @"
{
"asset": {
"state": {
"name": "In Store",
"id": "1"
},
"location": "Test Location"
}
}
"@
$header = @{TECHNICIAN_KEY=$ApiKey}
$params = @{input_data=$input;format='json'}
$Uri = $SdpUri + "/api/v3/assets/$id"
$result = Invoke-RestMethod -Method PUT -Uri $Uri -Headers $header -Body $params -ContentType "application/x-www-form-urlencoded"