Glossary
agentic payments
The class of payment flows initiated and settled by autonomous AI agents on a user's behalf, distinct from human-initiated checkout flows.
A category-of-flow rather than a single protocol. The shared problem: a user delegates a task to an agent; the task requires paying for an API call, a piece of compute, a piece of content, or a third-party service; the agent must initiate and settle that payment without asking the user to type a card number on each call.
Three competing protocol stacks address it. x402 (Coinbase, May 2025)
uses HTTP 402 Payment Required with USDC stablecoin settlement.
L402 (Lightning Labs, March 2020) is the Lightning-native HTTP 402
predecessor. Google’s AP2 framework (September 2025) layers
cryptographically-signed payment authority on top of A2AprotocolsA Google-launched open protocol for agent-to-agent communication, letting agents from different vendors discover each other's capabilities and exchange structured messages.
Open full entry and MCPprotocolsAn open protocol from Anthropic that standardizes how language models discover and call external tools, data sources, and prompts via a small JSON-RPC interface.
Open full entry ,
focused on intent and authorization rather than rails.
The unsolved questions are economic and legal: who is liable when an agent overpays, how do refunds and disputes work for sub-cent metered calls, and how do enterprises grant agent-level spend authority. The protocols are racing ahead of the operational answers.