Payment API Errors

I am having an issue processing payments in a plugin I am developing. They are being sent to the transaction list as "Not processed." I am trying to use /checkout/transactions to charge the transactions, but this is what I'm getting back:

 [{"message":"Transaction is required.","error_name":"ChargeTransactionNullArgument","error_code":14,"raw_message":"Transaction is required."}]

This is what the body I am sending looks like:

{"authorization_token":<transaction token>,"amount":"25.00"}