Auto generating API keys using the Application Authentication Endpoint

I am trying to auto generate API keys from a woocommerce website , but I am getting an error like this :

name:"FetchError"
message:"invalid json response body at https:/...............
.............................reason: Unexpected token < in JSON at position 0"
type:"invalid-json"

this is the code I have used , i have changed website names to sample names :



        const store_url = 'https://sample.com/';
        const endpoint = 'wc-auth/v1/authorize';
        const query_string = new URLSearchParams([
            ['app_name', 'MyShoppingWebsite'],
            ['scope', 'read_write'],
            ['user_id', '123'],
            ['return_url', 'https://example.com/apipractice'],
            ['callback_url', 'https://example.com/apipractice']
        ]).toString();

        const url = store_url + endpoint + '?' + query_string;



this is run from another website . 
any help is appreciated , thank you !!