Shipment items item category can't be blank, but i sent a shipment items category

Hi there. I'm sending a test post with an item category, but i'm getting back an exception---CloudShipmentManagerError - action: create_by_api - Shipment items item category can't be blank. Can you help me figure out what's wrong with this test query?
request id 9e031636-1b3d-4790-b5d0-c2cd280b965d
Data structure:
{:platform_name=>"MyPlatform",
:platform_order_number=>"MyOrderNumber",
:destination_country_alpha2=>"US",
:destination_city=>"San Francsico",
:destination_postal_code=>"94110",
:destination_state=>"CA",
:destination_name=>"bobby_2",
:destination_address_line_1=>"24 Peters Ave",
:destination_address_line_2=>"",
:destination_phone_number=>"2038563234",
:destination_email_address=>"[email protected]",
:items=>
[{:description=>"KITTY",
:sku=>"KITTY",
:actual_weight=>5.0,
:height=>1,
:width=>1,
:length=>1,
:category=>"watches",
:declared_currency=>"USD",
:declared_customs_value=>5.0}]}