Agent-to-Agent Payment Protocols: Delegation and Settlement Mechanisms Beyond Crypto Rails

1. Overview

Agent-to-agent (A2A) commerce is moving from theoretical to operational in 2024–2025, driven by frameworks like Anthropic's Model Context Protocol (MCP), Google's A2A protocol announcement, and emerging payment standards from Stripe, Visa, and Mastercard targeting autonomous AI buyers. The dominant architectural pattern is not trustless on-chain settlement but rather off-chain delegated authority backed by traditional payment rails, with crypto micropayments occupying a niche for sub-cent transactions and pseudonymous agents. The unsolved problems — capability attestation, dispute resolution at machine speed, and reputation portability — are precisely where infrastructure plays like Empirica's structured research API can establish trust primitives before the standards layer freezes.

This note extends Empirica's prior coverage of on-chain agent payments and research subscription consumption by mapping the full settlement stack: delegation protocols, authorisation patterns, escrow models, reputation signals, and the implementation gaps that block production deployment at scale.