AccountManager.java

@RestResource(urlMapping='/Accounts/*')
global with sharing class AccountManager {

    @HttpGet
    global static Account getAccountById() {
        RestRequest request = RestContext.request;
        String accountId = request.requestURI.substring(
          request.requestURI.lastIndexOf('/')+1);
        Account result =  [SELECT Name,AccountNumber,Type,BillingAddress
                        FROM Account
                        WHERE Id = :accountId];
        return result;
    }
    
     @HttpPost
    global static ID createAccount(String Name,String accountNumber) {
        Account thisAccount= new Account(
            Name=Name, AccountNumber = accountNumber);
        insert thisAccount;
        return thisAccount.Id;
    } 
}