Hearth: x402 Pay-Safety & Discovery MCP Server

ERC20 token balance on Base. ERC20 balance of any wallet on Base, Ethereum, Arbitrum or Optimism (USDC by default) via balanceOf, with decimals applied. Deterministic, no LLM. Example output: {"chain":"base","wallet":"0x…","token":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","raw":"1500000","decimals":6,"balance":"1.5"}. Price: $0.0025 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

ERC20 token metadata on Base. Name, symbol, decimals, total supply and bytecode presence for a token contract on Base, Ethereum, Arbitrum or Optimism. Deterministic, no LLM. Example output: {"chain":"base","address":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","name":"USD Coin","symbol":"USDC","decimals":6,"totalSupply":"…","isContract":true}. Price: $0.004 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Transaction status on Base. Status of a transaction on Base, Ethereum, Arbitrum or Optimism: pending/success/failed, block, confirmations, from/to, gas used, log count. Deterministic, no LLM. Example output: {"chain":"base","hash":"0x…","status":"success","blockNumber":1,"confirmations":10,"from":"0x…","to":"0x…","gasUsed":"21000","logs":0}. Price: $0.004 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Wallet snapshot on Base. Native ETH balance, nonce (tx count) and whether the address is a contract, on Base, Ethereum, Arbitrum or Optimism. Deterministic, no LLM. Example output: {"chain":"base","address":"0x…","ethWei":"0","eth":"0","nonce":0,"isContract":false,"block":1}. Price: $0.0025 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Base wallet intelligence: holdings, activity, counterparties, labels. One-call Base wallet profile: ETH and major token holdings (USDC, WETH, USDT, DAI, cbBTC, cbETH, AERO, EURC) with USD values, total USD, nonce (lifetime sent tx count), EOA vs contract (incl. EIP-7702 smart account), recent ERC20 transfers in/out over ~5,000 blocks (~3h) with net flow, top counterparties labeled where known (Uniswap, Aerodrome, 1inch, 0x, Aave, Seaport, bridges), and a simple wallet type. Free public data, deterministic, no LLM. Example output: {"address":"0x…","isContract":false,"nonce":1200,"ethBalance":"0.5","totalUsd":2100.4,"holdings":[{"symbol":"USDC","amount":"900","usd":900}],"recent":{"blocks":5000,"transfersIn":3,"transfersOut":5},"counterparties":[{"address":"0x6ff5…","label":"Uniswap Universal Router","count":4}],"walletType":". Price: $0.012 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Find the best x402 API for a task (ranked by real paying usage). Describe what you need (e.g. 'token holder analysis on base', 'web search', 'flight prices') and get the top x402 endpoints ranked by relevance and REAL payer quality: 30-day unique paying wallets, calls per payer (repeat usage), recency. Filters out unused, keep-alive self-paid and wallet-farmed listings that inflate the free catalog search. Covers Coinbase Bazaar + PayAI, refreshed nightly. Returns URL, price, method, input schema/example, networks, payTo, usage stats and a LIVE 402 probe per pick (dead endpoints sink). $0.005. Optional maxPrice (USD) and network filters. Example output: {"q":"web search","results":[{"url":"https://…/search","priceUsd":0.01,"usage30d":{"payers":120,"calls":4000,"callsPerPayer":33.3},"signal":"organic repeat usage"}]}. Price: $0.005 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

x402 pre-payment safety check: pay / caution / avoid. Before your agent pays an unknown x402 endpoint, check it ($0.005). Give an x402 URL and/or payTo; optional maxPrice to catch bait-and-switch. Live unpaid probe (GET then POST) parsing x402 v1 body AND v2 header; canonical USDC contract, network, price, timeout; payTo hijack / v1-v2 mismatch; payTo wallet on Base: ~75h of USDC inflows, distinct payers, self-funding concentration, fresh-wallet; Coinbase Bazaar + PayAI 30-day payers/calls with wallet-farming, keep-alive self-payment and listing-carpet detection; price vs median of comparable paid listings. Returns schema hearth.precheck.v2: verdict (pay/caution/avoid), allow, 0-100 score, confidence, coded reasons [{code,severity,detail}] and signals. Batch: /v1/x402/precheck-batch. Example output: {"schema":"hearth.precheck.v2","verdict":"pay","allow":true,"score":90,"confidence":"high","reasons":[],"signals":[{"code":"valid_402","severity":"info","detail":"valid x402 v2 challenge via POST"},{"code":"organic_catalog_usage","severity":"info","detail":"92 payers / 8960 calls in 30d"}],"priceUsd. Price: $0.005 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Batch x402 precheck: up to 10 URLs in one call. Run the full hearth.precheck.v2 check on up to 10 x402 URLs at once ($0.025, i.e. $0.0025 each). Pass urls as a comma-separated list (or JSON body {"urls": "a,b"}). Returns one result per URL plus a summary of pay/caution/avoid counts. Example output: {"count":2,"summary":{"pay":2,"caution":0,"avoid":0},"results":[{"url":"https://api.exa.ai/search","verdict":"pay","score":90}]}. Price: $0.025 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

x402 seller listing audit: spec compliance, discoverability, buyer-trust score + prioritized fixes. For people who SELL x402 endpoints. Give your endpoint URL; Hearth probes it unpaid (GET, falls back to POST) and grades it 0-100 (A-F) on 23 checks that decide whether agents can find, trust and pay you: HTTP 402, x402 v2 PAYMENT-REQUIRED header AND v1 body, Base option, canonical USDC, EIP-3009 extra, payTo, price, timeout, description quality, resource URL, input schema, output example, Bazaar discoverability extension, CORS expose headers, challenge latency, /.well-known/x402, /openapi.json, /llms.txt, robots.txt, Coinbase Bazaar/PayAI listing and real 30-day payers, and price vs comparable paid listings. Includes the full buyer-side safety verdict that agents (and Hearth's router) see for you, plus an AI-written, prioritized fix plan with concrete snippets. Free sample (score + failed check ids): /v1/free/seller-audit. Example output: {"schema":"hearth.seller-audit.v1","url":"https://seller.example/api/x","score":72,"grade":"C","passed":17,"failed":6,"topFixes":[{"title":"Add an input schema","why":"…","how":"…"}],"checks":[{"id":"status_402","ok":true,"weight":15,"detail":"unpaid GET returned HTTP 402"}],"buyerSafety":{"verdict". Price: $0.1 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Ranked x402 seller quality scores by category. Hearth's seller ranking data, per category (search, scrape, llm, image, enrich, onchain, price, social, weather, geo, audio, security) or free-text q: blended rank score with its parts, 30d paying usage, Hearth's own purchase outcomes (valid-response rate, latency), nightly liveness/payTo probe, and public reputation (402index reliability/uptime, vet402 verdict and settlement record, x402-trust grade), plus drop reasons. $0.005. Free sample: /v1/free/seller-scores?category=search Example output: {"schema":"hearth.seller-scores.v1","category":"search","sellers":[{"url":"https://seller.example/search","priceUsd":0.005,"rankScore":6.1,"recommended":true,"scoreParts":{"relevanceAndUsage":4.9,"index402":0.9,"trust":0.5}}]}. Price: $0.005 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Latest block or block by number. Block number, timestamp, hash, tx count, gas used/limit and base fee for the latest (or given) block on Base, Ethereum, Arbitrum or Optimism. Deterministic, no LLM. Example output: {"chain":"base","number":1,"hash":"0x…","timestamp":1700000000,"iso":"2026-01-01T00:00:00.000Z","txCount":100,"gasUsed":"1","gasLimit":"1","baseFeeGwei":"0.01"}. Price: $0.001 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Batch: up to 10 blocks in one call. Batch block lookup: latest block plus up to 10 block numbers (comma-separated) on Base, Ethereum, Arbitrum or Optimism in one paid call. Same fields as /v1/evm/block (number, hash, timestamp, tx count, gas, base fee). Costs less than 10 single calls. Deterministic, no LLM. Example output: {"chain":"base","latest":1,"blocks":[{"number":1,"hash":"0x…","timestamp":1700000000,"iso":"2026-01-01T00:00:00.000Z","txCount":100,"gasUsed":"1","gasLimit":"1","baseFeeGwei":"0.01"}]}. Price: $0.003 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Gas price and fee estimate. Current gas price, base fee, suggested priority fee and EIP-1559 maxFee for Base, Ethereum, Arbitrum or Optimism, plus a 21000-gas transfer cost in native units. Deterministic, no LLM. Example output: {"chain":"base","block":1,"gasPriceGwei":"0.01","baseFeeGwei":"0.005","priorityFeeGwei":"0.001","maxFeeGwei":"0.011","transferCostEth":"0.00000021"}. Price: $0.001 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Token USD price. Current USD price for a token contract on Base, Ethereum, Arbitrum or Optimism (or the chain's native ETH if no address), with symbol, decimals and confidence. Aggregated from public DeFi price feeds. Deterministic, no LLM. Example output: {"chain":"base","address":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","symbol":"USDC","priceUsd":0.9997,"decimals":6,"confidence":0.99,"timestamp":1700000000}. Price: $0.0035 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Token safety / honeypot / rug-risk check. Scam check for an ERC20 on Base, Ethereum, Arbitrum or Optimism: honeypot, buy/sell tax, mintable, owner can change balances, proxy, blacklist, open source, holder concentration, LP lock. Returns a 0-100 risk score, a verdict (low/medium/high) and the flags behind it. Use before buying or accepting a token. Deterministic, no LLM. Example output: {"chain":"base","address":"0x8335…2913","name":"USD Coin","symbol":"USDC","riskScore":5,"verdict":"low","flags":["proxy contract"],"buyTax":0,"sellTax":0,"holders":11378198,"top10HolderPercent":41.2,"isHoneypot":false,"source":"goplus+onchain"}. Price: $0.009 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Recent ERC20 transfers for a token or wallet. Recent ERC20 Transfer events (decoded: from, to, amount with decimals, symbol, tx hash, block) for a token contract, a wallet, or both, over the last ~2,000 blocks on Base, Arbitrum or Optimism (~500 on Ethereum). Up to 50 newest. Deterministic, no LLM. Example output: {"chain":"base","fromBlock":1,"toBlock":2,"count":1,"transfers":[{"token":"0x…","symbol":"USDC","from":"0x…","to":"0x…","amount":"12.5","tx":"0x…","block":2}]}. Price: $0.0045 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

NFT metadata. tokenURI and resolved JSON metadata (name, description, image, attributes) for an ERC-721 or ERC-1155 token on Base, Ethereum, Arbitrum or Optimism. IPFS/Arweave resolved. Deterministic, no LLM. Example output: {"chain":"base","contract":"0x…","tokenId":"1","tokenUri":"ipfs://…","metadata":{"name":"…","image":"ipfs://…","imageUrl":"https://ipfs.io/ipfs/…","attributes":[]}}. Price: $0.007 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

NFT owner (ERC-721). Current owner of an ERC-721 token (ownerOf) on Base, Ethereum, Arbitrum or Optimism. Deterministic, no LLM. Example output: {"chain":"base","contract":"0x…","tokenId":"1","owner":"0x…"}. Price: $0.0025 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Full token / contract due-diligence report (risk score + AI analyst write-up). One call, full due diligence on an ERC20 on Base, Ethereum, Arbitrum or Optimism before you buy, list, accept or integrate it. Combines: honeypot/tax/mint/blacklist/hidden-owner scan with 0-100 risk score; owner & creator holdings and whether ownership can be reclaimed; proxy/upgradeability and implementation; source verification (Sourcify) and privileged admin functions found in the ABI (mint, pause, blacklist, setFee, upgradeTo…); top-10 holders with locked/contract tags; DEX pools with USD liquidity and % of LP locked; USD price and approx market cap; recent on-chain transfer activity. Then an AI analyst write-up: verdict (avoid/caution/acceptable), key risks ranked, green flags, and what to verify next. Facts and write-up are both returned so you can audit the reasoning. Not charged if the token can't be analyzed. Free sample: /v1/free/token-report. Example output: {"schema":"hearth.token-report.v1","chain":"base","address":"0x4ed4…efed","verdict":"caution","riskScore":20,"headline":"Liquid meme token with no mint or tax traps; concentrated holders.","keyRisks":[{"risk":"…","severity":"medium","evidence":"…"}],"greenFlags":["…"],"verifyNext":["…"],"facts":{"to. Price: $0.25 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Wallet / counterparty intelligence dossier (risk flags + AI profile). Know who you're dealing with before you pay, accept funds from, or trade with an EVM address. One call combines: GoPlus security flags on Ethereum and Base (phishing, sanctioned, mixer, theft, fake-token, darkweb links…); multi-chain holdings with USD values (Base/Ethereum/Arbitrum/Optimism); account age signals (nonce, contract or EOA) on Base and Ethereum; ENS primary name; recent ERC20 transfers and top counterparties; and whether the address is an x402 seller (listings, 30-day payers/calls from Coinbase Bazaar + PayAI). Then an AI analyst profile: what kind of wallet this likely is, risk level (high/medium/low) with evidence, and recommended action. Facts are returned with the write-up. No private labels (unlike Arkham); everything is from public data. Free sample: /v1/free/wallet-report. Example output: {"schema":"hearth.wallet-report.v1","address":"0xd8dA…6045","riskLevel":"low","profile":"Long-lived, high-value individual wallet (vitalik.eth)…","evidence":["…"],"recommendation":"…","facts":{"ensName":"vitalik.eth","holdings":{},"securityFlags":[],"topCounterparties":[],"x402Seller":null}}. Price: $0.1 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Buy any x402 API through Hearth (standard: sellers up to $0.008). One call, any capability: describe what you need (q) and optional input (params JSON). Hearth classifies the intent (search, scrape, llm, image, enrich, onchain, price, social, geo, audio, security…), ranks verified x402 sellers by real paying usage, Hearth's own purchase outcomes, nightly free liveness probes and public reputation (402index reliability, vet402 verdicts and settlement, x402-trust grades), runs its pay-safety precheck (only 'pay'; payTo must match the verified listing; canonical USDC on Base), pays the seller from Hearth's wallet and returns the seller's response plus provenance. Flat $0.01; covers sellers up to $0.008. Not charged unless you get a result. Free preview: /v1/free/route?q=... Example output: {"schema":"hearth.route.v1","category":"search","seller":{"url":"https://seller.example/api/search","priceUsd":0.005,"payTo":"0x…","precheckScore":90,"rankScore":6.2,"tx":"0x…"},"contentType":"application/json","result":{"results":[]},"hearthPriceUsd":0.01}. Price: $0.01 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Buy any x402 API through Hearth (plus: sellers up to $0.05). One call, any capability: describe what you need (q) and optional input (params JSON). Hearth classifies the intent (search, scrape, llm, image, enrich, onchain, price, social, geo, audio, security…), ranks verified x402 sellers by real paying usage, Hearth's own purchase outcomes, nightly free liveness probes and public reputation (402index reliability, vet402 verdicts and settlement, x402-trust grades), runs its pay-safety precheck (only 'pay'; payTo must match the verified listing; canonical USDC on Base), pays the seller from Hearth's wallet and returns the seller's response plus provenance. Flat $0.06; covers sellers up to $0.05. Not charged unless you get a result. Free preview: /v1/free/route?q=... Example output: {"schema":"hearth.route.v1","category":"search","seller":{"url":"https://seller.example/api/search","priceUsd":0.005,"payTo":"0x…","precheckScore":90,"rankScore":6.2,"tx":"0x…"},"contentType":"application/json","result":{"results":[]},"hearthPriceUsd":0.06}. Price: $0.06 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Solana SOL balance. Native SOL balance (lamports and SOL) for any Solana address. Deterministic, no LLM. Example output: {"chain":"solana","address":"…","lamports":1000000000,"sol":"1","slot":1}. Price: $0.0025 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Solana wallet intelligence: holdings, activity, counterparties, programs. One-call Solana wallet profile: SOL and SPL/Token-2022 holdings with USD values (top 25 by value), total USD, recent activity (last 100 signatures: count, failure rate, first/last seen, tx per day), programs used with labels (Jupiter, Raydium, Orca, Pump.fun, Meteora, Drift...), top counterparties from the last 15 transactions, and a simple wallet type (bot-like / trader / holder / inactive). Free public data, deterministic, no LLM. Cheaper than comparable Solana wallet-intel APIs. Example output: {"address":"…","solBalance":1.2,"totalUsd":512.3,"holdings":[{"mint":"EPjF…","symbol":"USDC","amount":300,"usd":300}],"activity":{"sampled":100,"failed":2,"txPerDay":4.1,"lastSeen":"2026-10-27T18:00:00Z"},"programs":[{"id":"JUP6…","label":"Jupiter v6","count":8}],"counterparties":[{"address":"…","co. Price: $0.012 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Cheap LLM chat completion (flat $0.002). One-shot LLM completion for agents: send a prompt (and optional system message), get the answer text. Flat $0.002 per call, no account or API key; cheaper than typical x402 chat proxies. Up to ~2,000 chars of prompt and 600 output tokens. GET or POST JSON {prompt, system}. Example output: {"model":"gpt-5-nano","text":"bullish","usage":{"promptTokens":30,"completionTokens":2}}. Price: $0.002 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Company / domain enrichment from its website. Enrich a company domain: name, title, description, social profiles (LinkedIn, X, GitHub, etc.), contact emails and phones found on the homepage, language, tech hints (frameworks, analytics), mail provider from MX records, and key pages (about, pricing, careers, contact). Deterministic, no LLM, public data only. Example output: {"domain":"stripe.com","name":"Stripe","description":"Financial infrastructure...","socials":{"linkedin":"https://www.linkedin.com/company/stripe"},"emails":[],"mailProvider":"google","tech":["next.js"],"pages":{"pricing":"https://stripe.com/pricing"}}. Price: $0.01 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Contract verification and ABI. Whether a contract on Base, Ethereum, Arbitrum or Optimism is source-verified (Sourcify), its name, compiler, full ABI, function and event signatures, and its EIP-1967 proxy implementation (also looked up). Deterministic, no LLM. Example output: {"chain":"base","address":"0x…","isContract":true,"verified":true,"match":"exact_match","name":"FiatTokenProxy","compiler":"0.6.12","proxyImplementation":"0x…","functions":["admin()"],"events":["Upgraded(address)"],"abi":[]}. Price: $0.004 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

DEX swap quote (Uniswap v3). Best Uniswap v3 single-hop quote for swapping amountIn of tokenIn to tokenOut on Base, Ethereum, Arbitrum or Optimism, checking all fee tiers (0.01/0.05/0.3/1%). Returns amountOut, effective price, best fee tier, gas estimate. Tokens: ETH, USDC, USDT or 0x address. Read-only quote; no swap is executed. Deterministic, no LLM. Example output: {"chain":"base","tokenIn":"WETH","tokenOut":"USDC","amountIn":"1","amountOut":"2325.41","price":2325.41,"feeTier":500,"gasEstimate":"90000","venue":"uniswap-v3"}. Price: $0.0045 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Explain a transaction in plain English (AI). Plain-English explanation of any transaction on Base, Ethereum, Arbitrum or Optimism: what happened, who sent what to whom (decoded token transfers with amounts and symbols), the method called, fee paid, and success/failure. Returns a summary plus the structured facts it is based on. Example output: {"chain":"base","hash":"0x…","summary":"Wallet 0xa729… sent 0.0009 USDC to 0x1074… (an x402 payment), settled by a facilitator. Succeeded; fee ~$0.0001.","facts":{"status":"success","method":"0xe3ee160e","transfers":[]}}. Price: $0.015 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Extract structured JSON from a web page (AI). Fetch a public web page and extract the fields you name into clean JSON (e.g. fields=name,price,currency,availability or company,ceo,founded). Missing values come back as null. Up to 20 fields. Example output: {"url":"https://example.com","data":{"title":"Example Domain","contact_email":null,"description":"…"}}. Price: $0.02 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

GitHub repo stats and latest release. GitHub repository snapshot: stars, forks, open issues, watchers, language, license, topics, created/pushed dates, default branch, latest release (tag, date) and archived flag. Deterministic, no LLM. Example output: {"repo":"coinbase/x402","stars":1000,"forks":200,"openIssues":50,"language":"TypeScript","license":"Apache-2.0","latestRelease":{"tag":"v1.0.0","publishedAt":"2026-01-01T00:00:00Z"}}. Price: $0.003 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Crypto market overview: total cap, dominance, trending. Crypto market snapshot: total market cap and 24h volume (USD), 24h market-cap change, BTC/ETH dominance, active coins, plus the top trending coins (name, symbol, market-cap rank, price, 24h change). Deterministic, no LLM. Example output: {"totalMarketCapUsd":3100000000000,"totalVolumeUsd":120000000000,"marketCapChange24hPct":-0.8,"dominance":{"btc":57.1,"eth":11.9},"trending":[{"name":"Bitcoin","symbol":"BTC","rank":1,"priceUsd":100000,"change24hPct":1.2}]}. Price: $0.004 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

ENS / Basename resolve. Resolve an ENS name (vitalik.eth) or Basename (jesse.base.eth) to an address, or an address to its verified primary ENS name. On-chain, deterministic, no LLM. Example output: {"input":"vitalik.eth","name":"vitalik.eth","address":"0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045","registry":"ethereum"}. Price: $0.0045 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Hacker News search (stories and comments). Search Hacker News stories or comments by keyword, newest or most relevant first, with points, comment count, author, URL and HN link. Good for tracking mentions of a product, company or topic. Deterministic, no LLM. Example output: {"q":"x402","count":1,"hits":[{"title":"...","url":"...","points":12,"comments":3,"author":"pg","createdAt":"2026-01-01T00:00:00Z","hn":"https://news.ycombinator.com/item?id=1"}]}. Price: $0.003 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Summarize a web page (AI). Fetch a public web page and return a concise summary: title, 3-7 key points, a one-paragraph TL;DR and the page's main entities. Good for research agents that need the gist of a URL cheaply. Example output: {"url":"https://example.com","title":"Example Domain","tldr":"…","keyPoints":["…"],"entities":["IANA"]}. Price: $0.015 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).

Multi-chain wallet portfolio with USD values. One call: ETH, WETH, USDC and USDT balances for an address across Base, Ethereum, Arbitrum and Optimism, each with a USD value, plus the total USD value and per-chain subtotals. Deterministic, no LLM. Example output: {"address":"0xd8dA…6045","totalUsd":15234.12,"chains":{"base":{"usd":120.5,"assets":[{"symbol":"ETH","amount":"0.05","usd":116.3}]}},"ethPriceUsd":2326}. Price: $0.008 USDC on Base via x402 (pass the payment in _meta["x402/payment"]).