You don't need a key to use Pulse — it's free and works with no account. A key just
lets you use it in your own code (and is how Pro applies a higher rate limit). Email only, no card.
Your API key — shown once, save it
Send it as a header: Authorization: Bearer <key> on your /metrics calls.
Pro ($19/mo, higher rate limit) is being wired up — your free key works fully today.