{"id":"f0f03298-0b84-4797-95a8-327735bdf938","shortId":"eW8Yt2","kind":"x402","title":"Pay-per-call API platform on Base (USDC) offering data, AI, finance, and utility endpoints at $0.02/request.","tagline":"Pay-per-call API platform on Base (USDC) offering data, AI, finance, and utility endpoints at $0.02/request.","description":"lowpaymentfee.com is an x402-enabled API platform that exposes a broad catalog of pay-per-request endpoints settled in USDC on the Base network. The specific endpoint at `/api/v1/inbox/29` is listed as \"Premium API Access\" and costs up to $0.02 per call (20,000 base units of USDC with 6 decimals). Payment is handled via the x402 protocol — no API keys, no subscriptions, no rate limits. Callers attach an `X-PAYMENT` header with a valid payment proof and receive the response immediately.\n\nThe wider platform advertises four endpoint families: Data & Analytics (metrics, reports, data export, insights), AI & Machine Learning (sentiment analysis, text summarization, classification, embeddings), Finance & Web3 (price feeds, exchange rates, token quotes, gas estimates), and Infrastructure utilities (geocoding, validation, conversion, generation). All endpoints are listed at the same $0.02/request price point.\n\nHowever, the specific endpoint probed here (`/api/v1/inbox/29`) does not clearly map to any of the advertised categories. Its description is simply \"Premium API Access\" with no further documentation on what it returns. There is no OpenAPI spec, no request/response examples, and the crawled docs pages (pricing, README, API) all resolve to a minimal \"Connect wallet\" page with no additional content. The endpoint is live and returns a well-formed x402 challenge, but the actual functionality behind this particular path is undocumented.","tags":[],"capabilities":["x402-payment","usdc-base","pay-per-request","no-api-key","post-endpoint","json-response"],"categories":["api-platform","infrastructure"],"synonyms":["x402 API","micropayment API","USDC pay-per-call","Base network API","lowpaymentfee","low payment fee API","crypto API gateway"],"warnings":["The specific endpoint /api/v1/inbox/29 is not listed among the advertised API categories on the landing page — its actual functionality is unknown.","No OpenAPI spec, request schema, or response examples are available.","Documentation pages (/api, /pricing, /README) all resolve to a minimal 'Connect wallet' page with no useful content.","Without knowing what this endpoint returns, callers risk paying $0.02 for an unknown response."],"endpointUrl":"https://lowpaymentfee.com/api/v1/inbox/29","protocol":"x402","transport":"http","auth":{"type":"x402","details":[{"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","extra":{"name":"USD Coin","version":"2"},"payTo":"0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3","scheme":"exact","network":"base","mimeType":"application/json","resource":"https://lowpaymentfee.com/api/v1/inbox/29","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.300","qualityRationale":"The endpoint is live and returns a valid x402 challenge, but there is no OpenAPI spec, no request/response schema, and no documentation explaining what /api/v1/inbox/29 actually does. The crawled pages beyond the landing page are empty. The listing is effectively a stub with confirmed liveness and 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'/request':19,38,172 '0.02':18,37,80,171 '000':84 '20':83 '6':90 'Base network API' 'USDC pay-per-call' 'access':75,198 'actual':249 'addit':233 'advertis':127,190 'ai':12,31,138 'analysi':142 'analyt':132 'api':5,24,45,74,100,197,222 'attach':108 'base':8,27,63,85 'behind':251 'broad':50 'call':4,23,82 'caller':107 'catalog':51 'categori':191 'challeng':246 'classif':145 'clear':184 'connect':228 'content':234 'convers':162 'cost':77 'crawl':217 'crypto API gateway' 'data':11,30,131,135 'decim':91 'descript':193 'doc':218 'document':202 'embed':146 'enabl':44 'endpoint':16,35,57,67,129,165,178,236 'estim':156 'exampl':214 'exchang':151 'export':136 'expos':48 'famili':130 'feed':150 'financ':13,32,147 'form':244 'four':128 'function':250 'gas':155 'generat':163 'geocod':160 'handl':94 'header':113 'howev':175 'immedi':123 'infrastructur':158 'insight':137 'json-response' 'key':101 'learn':140 'limit':106 'list':71,167 'live':238 'low payment fee API' 'lowpaymentfee' 'lowpaymentfee.com':39 'machin':139 'map':185 'metric':133 'micropayment API' 'minim':227 'network':64 'no-api-key' 'offer':10,29 'openapi':210 'page':219,230 'particular':253 'path':254 'pay':2,21,54 'pay-per-cal':1,20 'pay-per-request':53 'payment':92,112,117 'per':3,22,55,81 'platform':6,25,46,126 'point':174 'post-endpoint' 'premium':73,196 'price':149,173,220 'probe':179 'proof':118 'protocol':98 'quot':154 'rate':105,152 'readm':221 'receiv':120 'report':134 'request':56 'request/response':213 'resolv':224 'respons':122 'return':206,240 'sentiment':141 'settl':58 'simpli':195 'spec':211 'specif':66,177 'subscript':103 'summar':144 'text':143 'token':153 'undocu':256 'unit':86 'usdc':9,28,60,88 'usdc-base' 'util':15,34,159 'valid':116,161 'via':95 'wallet':229 'web3':148 'well':243 'well-form':242 'wider':125 'x':111 'x-payment':110 'x402':43,97,245 'x402 API' 'x402-enabled':42 'x402-payment'","prices":[{"id":"431327ab-fe99-4a44-9b16-824c8353fc24","listingId":"f0f03298-0b84-4797-95a8-327735bdf938","amountUsd":null,"unit":"per_call","nativeCurrency":"USD COIN","nativeAmount":"20000","chain":"base","payTo":"0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3","paymentMethod":"x402-usd coin","isPrimary":true,"details":{"scheme":"exact","mime_type":"application/json","accepts_all":[{"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","extra":{"name":"USD Coin","version":"2"},"payTo":"0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3","scheme":"exact","network":"base","mimeType":"application/json","resource":"https://lowpaymentfee.com/api/v1/inbox/29","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-21T18:32:22.057Z"}],"sources":[{"listingId":"f0f03298-0b84-4797-95a8-327735bdf938","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/inbox/29","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:22.057Z","lastSeenAt":"2026-04-22T12:05:17.700Z"}],"details":{"listingId":"f0f03298-0b84-4797-95a8-327735bdf938","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/inbox/29 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <x402-payment-proof>\" \\\n  -d '{}'","exampleRequest":null,"exampleResponse":null,"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"The endpoint returns a valid x402 challenge with maxAmountRequired of 20000 base units of USDC on Base","source_url":"https://lowpaymentfee.com/api/v1/inbox/29"},{"claim":"USDC asset address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base network","source_url":"https://lowpaymentfee.com/api/v1/inbox/29"},{"claim":"Platform advertises $0.02/request pricing with no API keys, no rate limits, and instant access","source_url":"https://lowpaymentfee.com"},{"claim":"Four endpoint families listed: Data & Analytics, AI & Machine Learning, Finance & Web3, Infrastructure","source_url":"https://lowpaymentfee.com"}],"useCases":["Agent-driven API consumption with automatic per-call USDC payments","Accessing data, AI, or finance endpoints without managing API keys or subscriptions","Programmatic pay-as-you-go access to utility services on Base"],"bestFor":["Developers or agents wanting zero-signup, pay-per-call API access","x402-compatible clients that can settle USDC on Base","Low-volume or bursty workloads where subscription pricing is wasteful"],"notFor":["Users who need detailed API documentation or guaranteed SLAs before purchasing","High-volume consumers who would benefit from bulk/subscription pricing","Anyone unable to transact in USDC on the Base network"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:07.996Z"},"updatedAt":"2026-04-22T12:05:17.700Z"}}