Agent-to-Agent Mailbox (message passing) ($0.002/call)

Send data from one agent to another with no shared infrastructure. POST {channel, message} leaves JSON in a named mailbox; the receiving agent GETs ?channel= to pop it (FIFO). A scraper agent hands results to an analyst agent that runs an hour later; a pipeline passes work downstream — no queue to host, no server. Message up to 8KB, 1000 queued per channel.

Paid endpoint: $0.002 per call via the x402 protocol (USDC on Base). An unpaid request returns 402 with payment requirements in the PAYMENT-REQUIRED response header; attach payment and retry.