I built this as a collection of small API utilities I kept needing during development. It covers cron expression explaining, webhook inspection, DNS lookups, JSON formatting, hashing, base64, and regex testing. No auth required, no rate limits, totally free. Try it: curl https://frog03-20494.wykr.es/devtools/api/cron/explain?expr=...

The webhook inspector endpoint is probably the most useful one for me day-to-day. When debugging Stripe or GitHub webhook integrations, I used to spin up ngrok plus a local server just to see what payload format they actually send. Now I just POST to /devtools/api/hooks/create, get back a unique URL, point the webhook there, and GET the captured payloads. Dead simple and no signup required.