API keys are optional — /v1/* endpoints are publicly accessible without one. A key gives you a named rate-limit quota and usage tracking via X-RateLimit-* response headers.
Authorization: Bearer gca_your_key
X-API-Key: gca_your_key
Rate limit headers returned on every keyed request: X-RateLimit-Limit and X-RateLimit-Remaining. Quota resets at midnight UTC.
Full API reference →