Agent-to-Agent Payment Protocols: Task Delegation and Settlement in Autonomous Systems

1. Overview

Agent-to-agent (A2A) payment protocols are the connective tissue of the emerging agent economy: the mechanisms by which one autonomous AI system discovers, contracts with, invokes, and pays another for specialized work. As of late 2025 the landscape is fragmenting into three coexisting settlement rails — traditional API billing (postpaid, account-bound), prepaid credit balances with programmatic top-up, and on-chain micropayments using stablecoins, payment channels, and protocol-native tokens. The economic logic [P4] outlines for blockchains — radical reductions in verification and networking costs — applies with particular force when both counterparties are software, because the friction costs that justify human intermediaries (KYC, dispute resolution, relationship management) collapse when machine reputation and cryptographic proof suffice.

This synthesis maps the protocol stack (discovery → negotiation → execution → settlement), the economic patterns emerging within it, and where structured research products like Empirica's notes API fit into agent-readable commerce.