Glossary · x402, agents, and onchain payments

38 terms used in the lookx402 observatory, defined for humans and AI assistants. Each entry is marked up as schema.org/DefinedTerm for citation. Updated 2026-05-11.

Protocol & standards

x402: An open payment protocol introduced by Coinbase in 2025 that turns the HTTP 402 Payment Required status into a machine-to-machine payment standard. It lets autonomous programs (AI agents) pay for HTTP services with onchain stablecoins, without human approval. The reference implementation settles in USDC on Base.
EIP-3009: An Ethereum extension to ERC-20 that lets a token holder authorize a transfer with a signed off-chain message. Any third party (the facilitator) can submit the signed authorization on-chain. Used by Circle USDC and the foundation of x402 Path A on Base. See methodology §1.
EIP-712: The Ethereum typed-data signing standard that defines structured, human-readable signature payloads. EIP-3009 authorizations are signed as EIP-712 typed data, which lets wallets display the transfer parameters clearly to the user (or the agent's keystore).
Permit2: Uniswap's signature-based token approval contract. The x402 Path B variant routes payments through a Permit2 settle proxy at 0x402085c248EeA27D92E8b30b2C58ed07f9E20001. As of 2026-04 this path has effectively zero observed volume.
ERC-8004: A proposed Ethereum standard for an on-chain agent identity and reputation registry. AI agents can be registered with an owner address, metadata URI, and reputation attestations. lookx402 reads ERC-8004 mainnet entries for cross-reference enrichment.
AuthorizationUsed: The USDC ERC-3009 event emitted on every successful transferWithAuthorization / receiveWithAuthorization call. Signature topic 0x98de503528ee59b575ef0c0a2576a82497bfc029a5685b209e9ec333479b10a5. Its topics[1] is the indexed authorizer — the real payer of the x402 tx, not tx.from.
transferWithAuthorization: The ERC-3009 function that moves USDC from authorizer to recipient using an off-chain signed authorization. Selector 0xe3ee160e on Base USDC. The dominant x402 settlement primitive (~89% of observed volume).
receiveWithAuthorization: The ERC-3009 receive variant — the merchant pulls funds rather than the agent pushing. Selector 0xcf092995 on Base USDC. Used in a minority of x402 flows where the merchant collects.
nonce (EIP-3009): A 32-byte unique value embedded in every EIP-3009 authorization. The USDC contract refuses to settle the same (authorizer, nonce) pair twice. lookx402 indexes nonces to detect replay attempts and deduplicate ingestion.

Actors

AI agent: An autonomous program that has been granted a crypto wallet and the authority to spend on its own behalf — paying for online services such as LLM inference, search APIs, or compute, without per-call human approval. In x402 context, the agent is the EIP-3009 authorizer.
facilitator: An off-chain service (e.g. CDP, OpenFacilitator, Primer) that receives a signed EIP-3009 authorization from an agent, broadcasts it on-chain in a transaction, and pays the gas. The facilitator is NOT the agent — its wallet appears in tx.from, while the real payer is in topics[1] of the AuthorizationUsed event. Naive leaderboards that confuse the two rank facilitators as top agents.
CDP: Coinbase Developer Platform — Coinbase's reference x402 facilitator service. Its facilitator wallet appears as tx.from for a large fraction of observed x402 transactions, but it is never the actual payer.
OpenFacilitator: An independent, open-source x402 facilitator. Like CDP it appears as tx.from but is not the agent. lookx402 treats every known facilitator as a transparent relay.
anonymous merchant: A wallet that receives x402 payments but has no public label, no verified contract source, and no entry in published x402 partner directories (PayAI, Coinbase Commerce, Basescan tags). About 99% of observed merchants are anonymous as of 2026-04.

Concepts & metrics

agentic economy: The emerging economy of machine-to-machine payments where AI agents transact directly with online services, paying per-call in stablecoins. Sometimes called the M2M (machine-to-machine) economy. x402 is the dominant settlement layer for this economy on Base as of 2026.
M2M payment: Machine-to-machine payment — a transaction initiated and authorized by software without per-call human intervention. x402 is the leading open-protocol M2M payment standard on Ethereum L2s as of 2026.
USDC: USD Coin, the regulated stablecoin issued by Circle. On Base mainnet the canonical USDC contract is 0x833589fcd6edb6e08f4c7c32d4f71b54bda02913. 100% of observed x402 volume settles in USDC.
Base: Coinbase's Ethereum L2 rollup (chain id 8453) where the bulk of x402 traffic settles. Native to the Coinbase developer ecosystem and the default settlement layer for the x402 reference implementation.
atomic units (USDC): USDC has 6 decimals, so 1 USDC = 1,000,000 atomic units. lookx402 stores raw volume in atomic units (volume_atomic) and formats to USDC for display (volume_usdc = volume_atomic / 1e6).
dyad: In lookx402 terminology, a (payer, merchant) pair observed in our index. A dyad represents a recurring relationship between one agent and one service — e.g. a research bot calling the same Anthropic-tagged endpoint 200 times in a week.
whale: A single x402 transaction with a value of $100 USDC or more. Whales account for roughly 0.4% of tx count but ~90% of dollar volume on the x402 protocol.
marathon: A dyad with more than 100 transactions in our observation window. Marathons signal persistent service relationships rather than one-shot calls.

Behavioral archetypes

Full rules at /archetypes; live rankings per archetype at /agents/<archetype>.

archetype: In lookx402, a behavioral category assigned by an hourly classifier to every agent based on six signals: tx count, median amount, lifetime in days, distinct merchants, night-hour ratio, and cadence jitter. The current archetypes are sprinter, marathoner, ghost, burner, night_owl, worker_bee, hunter, drone, and unknown.
sprinter: An archetype: a wallet with ≥100 transactions in ≤1 day. Sprinters are burst-mode bots — concentrated activity in a short window. Live ranking →
marathoner: An archetype: a wallet with ≥200 transactions spread over ≥7 days. Marathoners represent sustained, programmatic spend — usually long-running services or scheduled jobs. Live ranking →
ghost: An archetype: a wallet with exactly one x402 transaction, ever. About 47% of classified agents are ghosts — disposable fire-and-forget identities, often a test, a one-off API call, or a wallet rotation pattern. Live ranking →
burner: An archetype: a wallet with 2 to 99 transactions, all within a single day. Burners look like short-lived, single-purpose identities — funded, used, retired. Live ranking →
night_owl: An archetype: a wallet whose ≥60% of transactions land in 22:00–06:00 UTC. Often signals automated batch jobs that run during off-peak hours, or operators in non-European timezones. Live ranking →
worker_bee: An archetype: ≥30 transactions across ≤3 distinct merchants. Focused, repeat-customer bots — likely a single agent powering one product flow. Live ranking →
hunter: An archetype: ≥30 transactions across ≥10 distinct merchants. Wide-footprint agents — explorers or orchestrators that hit many services. Common pattern for research/aggregation bots. Live ranking →
drone: An archetype: ≥10 transactions with median delay between consecutive tx of less than 60 seconds. Drones are tight-loop bots — likely streaming or polling workloads. Live ranking →

Ecosystem

PayAI: A directory of x402-enabled AI services maintained by the PayAI community. lookx402 seeds its merchant labels from PayAI's public list and from Coinbase's published x402 partner directory.
x402scan: A separate x402 explorer maintained by a different team. x402scan focuses on raw transaction tables for developers. lookx402 differentiates by aggregating per-agent profiles, dyads, and archetypes for journalists, researchers, and business users — see /vs/x402scan for a side-by-side.
facilitator economics: The cost and revenue structure of running an x402 facilitator service. Facilitators receive signed EIP-3009 authorizations from agents, pay Base mainnet gas to broadcast them on-chain (about $0.0001 per transaction at 2026 gas prices), and may charge agents a small fee or operate as loss-leader infrastructure. Coinbase Developer Platform, OpenFacilitator, and Primer are the three observed facilitators in lookx402 data.

Concepts (extended 2026-05-11)

agentic commerce: Commerce conducted by autonomous AI agents on behalf of users or organizations, where the agent itself selects, negotiates, and settles transactions with online services. Agentic commerce assumes per-call programmatic payment rails (such as x402 on Base) rather than human-approved checkout flows. As of 2026, lookx402 has indexed roughly 3.5 million agentic-commerce transactions cumulating around $80 million USDC in volume.
stablecoin micropayments: On-chain transfers of fiat-pegged stablecoin (typically USDC) for amounts well below one US dollar. Stablecoin micropayments are the economic primitive that x402 exposes over HTTP. The lookx402 dataset confirms median x402 transaction sizes around 0.001 USDC (one tenth of one cent), a price point traditional rails like Stripe cannot serve because their per-transaction fees exceed the payment itself.
agent identity vs operator identity: The distinction between the wallet that signs an x402 authorization (agent identity, recorded as the EIP-3009 authorizer in topics[1]) and the natural or legal person who controls or deployed that wallet (operator identity, off-chain and typically unknown). lookx402 only tracks agent identity. We do not chain-cluster agent wallets to operator identities and we treat the gap between the two as a privacy property to respect, not a puzzle to solve.
M2M monetization: A service business model where machine clients (AI agents) pay per call rather than human users paying per seat or subscription. M2M monetization assumes (a) a payment protocol that supports sub-cent transactions like x402, (b) HTTP-native price discovery via the 402 status code, and (c) on-chain settlement so the merchant can confirm payment before delivering content. lookx402 tracks the live M2M monetization layer of the agentic economy on Base.

All definitions are derived from on-chain data lookx402 observes on Base mainnet, the public x402 reference implementation, and the EIP texts. Citation is welcome — see methodology · how to cite.