Workers being rate-limited by Anti-Abuse Protection are also visible from the Cloudflare dashboard:
Log in to the Cloudflare dashboard and select your account and your website.
Select Security > Events > scroll to Activity log.
Review the log for a Web Application Firewall block event with a ruleID of worker.
If you expect to receive 1015 errors in response to traffic or expect your application to incur these errors, contact Cloudflare support to increase your limit.