Glossary

Term	Acronym	Definition	Synonym / Related
Agent Payments Protocol	AP2	An open protocol designed to enable AI agents to securely interoperate and complete payments autonomously.
Agent2Agent Protocol	A2A	An open standard for secure, collaborative communication and task management between diverse AI agents, regardless of their underlying frameworks. Context: AP2 can be implemented as an extension of A2A to facilitate financial transactions, with a focus on high-trust agentic payments.
Agentic payments		Payment flows in which autonomous AI Agents are involved.
Credentials Provider	CP	A secure entity, like a digital wallet, responsible for managing and executing the user's payment and identity credentials.
Deterministic cryptographical proof		A unique mathematical proof that could be linked to a hardware device.
Dynamic Linking		A core requirement for Strong Customer Authentication (SCA), involving the inclusion of specific transaction details within a Payment Credential to link the SCA to that transaction. Context: Ensures the payer explicitly consents to transaction details like amount and payee.
Merchant Endpoint (Or Remote Endpoint)	ME, RE	The web interface or AI agent representing the seller, showcasing products and negotiating the cart.
Merchant Payment Processor Endpoint	MPP	The entity responsible for constructing and sending the transaction authorization message to the payment ecosystem.
Model Context Protocol	MCP	A protocol standardizing how AI models and agents connect to and interact with external resources like tools, APIs, and data sources.
Payee		A person or entity who is the intended recipient of funds from a payment transaction. Context: Can request attestations along with payment confirmation.	Merchant, Creditor Name
Payer		A person or entity who holds a payment account, allows a payment order from that account. Context: Initiates payment orders.	User, Holder
Payment Agent		A proposed key role in agent payments responsible for selecting the ideal payment method, validating payment details, and handling errors. Context: A Payment Agent is not a necessary requirement to participate in the protocol. MCP-based endpoints can also play similar roles.
Payment Contracts		"Mandates" or "Payment Contracts" that capture a user's specific instructions to their agent. Context: Define principles for safe, secure, and high-trust agentic payments. They can be global or transaction-level.	Mandates, Shopping Mandate
Payment Credential		A credential or instrument (or reference to one) which can be charged towards a payment.	Electronic Attestation of Attributes (EAA), Payment Wallet Attestation (PWA), Digital Payment Credentials (DPC), Payment Means Attestation, SPC Credential
Payment Request API (W3C Standard)		A web API that acts as an intermediary between a merchant, user, and payment method provider to streamline the payment experience.
Strong Customer Authentication	SCA	A process required by regulatory frameworks for online identification and transaction initiation in financial services. Context: Central to the Payments Rulebook, ensuring security and dynamic linking of transactions.	Strong User Authentication, Integrated SCA
User		The human initiating the task and providing financial authority.
User Agent a.k.a. Shopping Agent	UA, SA	The AI surface interacts directly with the user, understanding their needs, and coordinating the purchase.
Verifiable Credential	VC	An Issuer-signed credential (i.e., a set of Claims) whose authenticity can be verified. Context: Typically bound to a cryptographic key and used in the issuer-holder-verifier model.	Digital Credential
Verifiable Presentation	VP	A presentation of one or more VCs that includes a cryptographic proof of holder binding, created in response to a request from a Verifier. Context: Allows a Verifier to confirm that the Holder intended the presentation for them and may reveal only a subset of claims.