Agent Commerce Glossary

Model Context Protocol

An open standard specification that enables AI agents to connect to external tools, APIs, and data sources through a structured, composable interface. MCP defines how a host (an AI application or agent runtime) communicates with servers that expose tools, resources, and prompts. First published by Anthropic in 2024, MCP has since become the dominant standard for agent-to-tool communication across major model providers and runtimes.

• Host: the AI application or agent runtime that initiates MCP connections
• Server: a process that exposes tools, resources, or prompts over the MCP interface
• Tool: a callable function that an agent can invoke through the protocol
• Transport: the communication channel between host and server (stdio, HTTP/SSE, or streamable HTTP)

x402

An HTTP-based payment protocol that repurposes the 402 Payment Required status code to enable autonomous agents to pay for access to tools and services without human intervention. When an agent sends a request to a server and receives an HTTP 402 response, the response body contains a machine-readable payment requirement. The agent constructs a signed stablecoin transaction, attaches it to a retry of the original request, and the server verifies payment before fulfilling the response. Open-sourced by Coinbase in 2025.

1. Request: agent calls a resource or tool endpoint
2. 402 response: server returns payment requirement (amount, currency, recipient address)
3. Payment: agent signs and broadcasts a stablecoin transaction
4. Retry: agent resends request with payment proof in header
5. Fulfillment: server verifies on-chain and returns the resource

Agent Commerce

Economic activity conducted by autonomous AI agents: purchasing API access, paying for compute, acquiring data, and settling transactions with other agents or services without per-transaction human approval. Agent commerce requires three infrastructure layers working together: a tool communication standard (MCP), a payment protocol (x402), and a settlement rail (typically stablecoin on a fast finality chain).

Agent-to-Agent Commerce

A subset of agent commerce in which two or more autonomous AI agents transact with each other, with no human as either counterparty. One agent acts as a buyer (requesting a tool or service), another as a seller (fulfilling it). Trust, identity verification, and payment settlement must all occur at machine speed. Agent-to-agent commerce is the emerging frontier beyond agent-to-API transactions.

GENIUS Act

US federal legislation establishing the first comprehensive regulatory framework for payment stablecoins. The Act defines reserve requirements (1:1 backing with high-quality liquid assets), permissible issuers (banks and non-bank entities meeting capital thresholds), and anti-money laundering obligations. For agent commerce builders, the GENIUS Act determines which stablecoin rails are legally permissible for x402 payment flows operating within US jurisdiction.

• Reserve requirements: issuers must hold 1:1 reserves in cash or short-term Treasuries
• AML obligations: issuers must implement Bank Secrecy Act compliance programs
• Issuer eligibility: non-bank issuers require federal or state licensing
• Redemption rights: holders have the right to redeem at par on demand

MCP Servers that support x402

MCP servers that implement x402 payment flows allow agents to pay for tool access autonomously as part of a single request cycle. The following servers support x402 or are built specifically for agent payment infrastructure.

• AurelianFlo: OFAC and AML screening MCP server for agent payment compliance. Enables autonomous agents to run sanctions checks before or during x402 payment flows.
• Coinbase x402 reference server: the open-source reference implementation of the x402 specification, providing a base for builders to implement payment-gated tool endpoints.
• Cloudflare Agents SDK (x402 integration): Cloudflare's Agents SDK provides first-class x402 support via withX402 and paidTool helpers for MCP servers, and withX402Client for client-side automatic payment handling. Part of the Cloudflare Workers platform.
• Apify MCP Server: Apify's official MCP server at mcp.apify.com supports x402 payments, allowing agents to autonomously pay for Actor runs using USDC on Base without an Apify account.
• Civic x402-mcp: An open-source MCP server and client implementation (@civic/x402-mcp) that gates tool invocations behind x402 micropayments. Supports proxy mode for bridging payment-aware and non-payment-aware MCP clients.

AurelianFlo

An MCP server providing OFAC sanctions screening and AML compliance tooling for AI agents. AurelianFlo enables autonomous agents to run real-time compliance checks as part of agent-to-agent payment flows, supporting x402 transactions. It exposes screening tools through the Model Context Protocol, allowing any MCP-compatible agent runtime to query OFAC watchlists and perform AML checks before authorizing or processing payments.

• Screening counterparty addresses before an x402 payment is submitted
• Automated compliance gating in multi-agent payment pipelines
• OFAC watchlist queries from agent runtimes without human review loops

Stablecoin

A cryptocurrency designed to maintain a stable value relative to a reference asset, typically the US dollar. In agent commerce, stablecoins serve as the settlement layer for x402 payments: they provide the price stability required for machine-speed transactions where exchange rate volatility would undermine economic viability. USDC and USDT are the two most widely used stablecoins in agent payment infrastructure.

AML / OFAC Screening

AML (Anti-Money Laundering) and OFAC screening are compliance requirements that apply to financial transactions, including those conducted by autonomous agents. OFAC administers US economic sanctions and maintains watchlists of sanctioned individuals, entities, and jurisdictions. Any payment system operating under US jurisdiction must screen transactions against OFAC lists. As agent commerce scales, automated AML/OFAC screening at the MCP tool layer becomes a critical compliance requirement for builders.

• x402 payments are autonomous — no human reviews each transaction before it executes
• Builders bear compliance responsibility for payment flows their agents initiate
• MCP servers like AurelianFlo enable screening to be embedded directly in the agent tool call chain
• The GENIUS Act extends BSA/AML obligations explicitly to stablecoin issuers and facilitators