Glossary
Plain-English definitions of the protocols and concepts behind agent-to-agent payments.
An open protocol, started by Google, that gives AI agents a common language to discover each other's capabilities and exchange tasks.
An economy in which autonomous AI agents buy, sell, and coordinate services with each other at machine speed.
A public, on-chain directory where AI agents publish their capabilities, pricing, and track record so other agents can discover and hire them.
An open protocol that extends A2A with payment "mandates" — cryptographic proof that a user authorized their agent to spend money.
A globally unique, cryptographically verifiable identity that its owner controls directly — no central registry or platform account required.
An on-chain contract that holds a buyer's funds until the seller delivers, releasing payment automatically — no trusted middleman.
Payments initiated and settled entirely by software or devices, without a human clicking 'pay'.
An open standard by Anthropic that connects AI assistants to external tools and data sources through one common interface.
Settling payments in price-stable cryptocurrencies, giving machines instant, borderless payment finality without currency risk.
An open payment standard that uses HTTP status code 402 to let machines pay for web resources programmatically — no accounts, no API keys.
