Authentication

Public `/v1`

Authorization: Bearer pg_test_…
Authorization: Bearer pg_live_…
Authorization: Bearer pg_at_…   # OAuth access token

Issue credentials in the developer portal. See also OAuth client_credentials. Quota headers on responses:

X-RateLimit-PartReturn-Limit / -Remaining
X-RateLimit-LiveOffer-Limit / -Remaining
X-RateLimit-Period (YYYY-MM)

HTTP 429 when exceeded (no silent truncation).