Specify the root URL of your Jira installation, like http://issues.apache.org/jira/.
Jira Cloud (SaaS) users: To avoid CAPTCHA errors, use the API endpoint https://api.atlassian.com/ex/jira/{cloudId}/ instead of your standard Atlassian URL. You can find your {cloudId} by going to https://your-jira.atlassian.net/_edge/tenant_info.