There are some headers that are mandatory in a REST API request, while others are optional. Here are some examples of mandatory headers that you should include in your REST API requests. In general, these headers are generated by the client sending the request.

Host: This header specifies the hostname of the server that the request is being sent to. It is mandatory in HTTP/1.1 and later versions of the protocol.
Content-Type: This header specifies the format of the data being sent in the request body. It is mandatory when the request includes a message body (such as with a POST or PUT request).
Content-Length: This header specifies the length of the message body in bytes. It is mandatory when the request includes a message body.

Host: api.sinay.ai
Content-Type: application/json
Content-Length: 411