Frequently asked questions
Agent402 is the open-source, self-hostable x402 + MCP server: an open cross-seller Index, Smart Order Router, and on-chain leaderboard, built on pay-per-call web tools for AI agents - free via proof-of-work or paid in USDC on Base, Solana, Polygon, Arbitrum, Monad, Celo, Avalanche, Sei, Optimism, Stellar & Algorand - plus USDG on Robinhood Chain.
Do I need an account or API key?+
No. Nothing here has a signup. Payment - USDC or proof-of-work - is the only credential, charged per call.
What does it cost?+
Flat per-call prices, $0.001–$0.02, published in /api/pricing and quoted exactly in every HTTP 402 response. No subscriptions or tiers.
Can I use it without any money or a wallet?+
Yes. Most pure-CPU tools accept proof-of-work - a sub-second sha256 puzzle solved by your own CPU - and the hosted MCP connector runs that same set for free (rate-limited).
What is x402?+
An open HTTP payment standard built on the 402 Payment Required status code, for machine-to-machine pay-per-call payments in stablecoins, with settlement infrastructure from Coinbase. Plain-English explainer: /what-is-x402.
What is MPP, and does Agent402 support it?+
Yes - every paid endpoint is dual-stack. MPP (Machine Payments Protocol, the IETF-track Payment HTTP authentication scheme) carries the same pay-per-call handshake through the web’s standard auth headers: the 402 carries a WWW-Authenticate: Payment challenge, the client pays via Authorization: Payment, and settled responses return a signed Payment-Receipt. Same URL, same price, same on-chain USDC settlement as x402 - the buyer’s client picks the dialect. How the two compare: /what-is-x402; the full MPP explainer: /what-is-mpp.
Which blockchain and asset does it use?+
USDC on Base (or Solana, Polygon, Arbitrum, Monad, Celo, Avalanche, Sei, Optimism, Stellar, Algorand - or USDG on Robinhood Chain). The buyer needs only the stablecoin - gas is sponsored by the facilitator on EVM chains.
Does using this spend my AI tokens?+
No LLM in the deterministic tool path - those are pure code (parsers, hashes, math, a real browser). Proof-of-work spends your CPU; x402 spends USDC. The optional /v1 gateway is a separate OpenAI-compatible LLM proxy you opt into - it's the only place a model runs.
Is there an OpenAI-compatible endpoint?+
Yes - /v1 is a pay-per-call OpenAI-wire LLM gateway: point any OpenAI SDK at base_url https://agent402.tools/v1 for chat (five quality tiers, model-optional auto-routing), embeddings, and image generation. No API key, no signup - settle in USDC over x402, same as every other tool. See /pricing for the tier breakdown.
Is my data stored?+
Tool inputs are processed in memory and not persisted - except the memory tools, whose purpose is storage (wallet-keyed, owner-deletable, with optional TTL). Full policy: /privacy.
How do I know the service is honest?+
It is fully open source; CI re-tests every endpoint against its own documented example before each deploy; and revenue settles on-chain to agent402.base.eth (the named public receiving wallet), auditable by anyone on Basescan.
What happens if a tool fails after I pay?+
You are not charged. Payment settles only for a successful (under-400) response, so an error cancels settlement and no money moves. On top of that guarantee, anything which can't be served reliably is removed from the catalog rather than left to fail, and failure rates are watched by CI and a 15-minute production heartbeat.
Is Agent402 self-hostable and open source?+
Yes - the server is open source under the AGPL-3.0 license (the client SDK, MCP connector, and tollbooth are MIT). Clone the repo and run it yourself for free, with or without payments enabled. It also ships agent402-tollbooth, an open-source pay-per-crawl gate for charging AI crawlers on your own site.
Can I find tools on other x402 sellers from here?+
Yes. Agent402 is also an x402 Index + Smart Order Router: POST /api/route ranks tools across every x402 seller we have crawled - the local catalog plus sellers auto-discovered from public registries like the Coinbase CDP Bazaar, refreshed hourly. It filters out unhealthy sellers and tiebreaks on health then price. Browse the live marketplace at /marketplace or fetch the JSON snapshot at /api/index. Both surfaces are free.
How do I list my own API?+
For free, three ways: your origin is auto-discovered from public x402 registries (Coinbase CDP Bazaar, GoPlausible) once it’s live and settling; paste it on /sell for an immediate probe; or call POST /api/index/register directly. A listed seller is routable by the Smart Order Router and ranked on /leaderboard by real on-chain USDC volume - 0% take, settlement lands straight in your wallet.
How do I see which x402 sellers are most used?+
GET /api/leaderboard returns the live on-chain ranking of every x402 seller by Base USDC settled volume - callsSettled, totalUsd, and uniqueBuyers per seller. The pipeline walks every page of the Coinbase CDP Bazaar discovery endpoint, queries eth_getLogs on Base USDC for each seller’s payTo, filters per-call settlements within a $0.50 ceiling (larger inbound is funding/swaps, not buys), and aggregates. The snapshot refreshes hourly server-side. Free, like /api/find and /api/route. Use ?include=external to exclude Agent402 itself and rank only the rest of the ecosystem.
How does the Smart Order Router decide which seller to route to?+
It scores tools by lexical match against your query, then ranks by seller health (computed from the last five crawl outcomes), then by price. Sellers whose recent crawls errored are excluded entirely - a buyer routed to a dead seller wastes money. Brand-new sellers with no history yet are still routable: benefit of the doubt for newcomers.
Who runs Agent402?+
Havok Holdings LLC - a public, contactable maintainer reachable at mike@agent402.tools, on GitHub, and on X.