No Validation Check on Mandatory Fields in WEB API

Hi CRM Team,

I am trying to Create Accounts and Contacts using REST APIs. I have couple of observations:
a) No Validation check on the mandatory fields
When I try to create an Account or Contact, if I use any property for the entity, the Account gets created successfully. I mean there is no validation for any mandatory field.
But on UI there are mandatory fields to create an Account like Account Name.

So is this a defect in the POST API? Could you please provide your inputs.

b) 204 Blank Response Body
When the Account/Contact is created successfully, the Response body is blank with status code as 204 No Content. Usually the response body displays the details of the Account/Contact which gets created successfully.

Could you please provide inputs for the above two observations.