Run up to 10 internal calls in one payment: POST {calls:[{path,input}]} and pay the SUM of the internal prices (≤ $0.05 total), executed in parallel, results returned in order. Batchable endpoints are the local, deterministic ones (validators, format transforms, time/locale) — no browser, network, composite or dynamic endpoints. Each result carries {path, status, body}; a bad request (unknown path, >10 calls, over cap) is a 400, not charged.