Scope: channel:read, channel:write, purchase-orders:write or admin.

Idempotency: not keyed; the request itself is safe to repeat.

Rate limit: read class, 6,000 requests per minute per tenant by default (write class 1,200). Every response carries X-RateLimit-Limit, X-RateLimit-Remaining and X-RateLimit-Reset; a refusal is 429 rate_limited with Retry-After.