Hide response returned from WordPress REST API call

Question

I have created this simple WordPress REST API where users can perform:

  Option A
• Types in the following URL in browser:
      → www.example.com/wp-json/v1/getBook/123456?AuthorSurname=Buckley
   The API will retrieve the relevant information and return a response in the browser:
      → {"Book":"Thank you for smoking"}

  Option B
• Perform a CURL statement in CMD or via scripting:
   (for Example)

function getBook($authorID, $authorSurname){  
    $ch = curl_init();
    $url = 'www.example.com/wp-json/v1/getBook/123456?AuthorSurname=Buckley';
    curl_setopt($ch, CURLOPT_HTTPHEADER, array('Accept:application/json','Content-Type:application/json'  ));
    curl_setopt($ch, CURLOPT_URL, $url.$authorID.'?AuthorSurname='.$authorSurname);
    curl_setopt($ch, CURLOPT_HEADER, 0);

    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

    //execute the POST request
    $result = curl_exec($ch);       
    return $result;

    curl_close($ch);
<br><br>

I would like to prevent the response from showing whenever user perform Option A.
The response can only be shown via Option B.

How can I achieve this?