APEX Rest Class

Update your code like below

public with sharing class AccountToFACustomer {
    public class Response{
        public integer code {get; set;}
        public String body {get; set;}
        public boolean success {get; set;}
        public String errorText {get; set;}
        public Response (integer code, String body){
                this.code = code;
        		this.body = body;
        		this.success = (code == 200 || code == 201);
        }
    }
    public class customerResponse{
        public string uuid {get; set;}
        public string link {get; set;}
        public string location {get; set;}
    }
    public Response CreateCustomer (string description){
        Response resp;
        string endpoint = 'https://apis.website.net/';
        string token = 'Token XXXXX';
        string method = 'POST';
        HttpRequest req = new HttpRequest();
        HttpResponse res = new HttpResponse();
        Http h = new http();
        req.setEndpoint(endpoint);
        req.setMethod(method);
        req.setHeader('Autorization', token);
		req.setHeader('Content-Type', 'application/json');
        req.setHeader('Accept-Type', 'application/json');
        req.setBody(
            '{"name":"'+ Account.Name +'","email":"'+ Account.Email__c + '",'+
             '"phone":"'+ Account.Phone +'",'+
             '"website":"'+ Account.Website +'",'+
             '"location":{'+
                 	'"name":"Account No: '+ Account.Sage_ID__c +'",'+
                    '"streetName":"'+ Account.BillingStreet +'",'+
                    '"locality":"'+ Account.BillingCity +'",'+
                    '"postcode":"'+ Account.BillingState +'",'+
                    '"country":"'+ Account.BillingCountry +'" }}' 
        );
        try{
		res = h.send(req);
        resp = new Response(res.getStatusCode(), res.getBody()); 
            if (resp.success) {
                customerResponse custResp = (customerResponse)JSON.deserialize(res.getBody(), customerResponse.class);
            }
        }
        	 catch(System.CalloutException e) {
   				 System.debug('Callout error: '+ e);
				 return resp;
        }        
        return resp;
    }
}