{"id":"01edf3cb-31a1-48a3-b4fa-a213a260acb6","shortId":"FEYfPx","kind":"x402","title":"Pay-per-call premium API access on Base via x402 — $0.02/request in USDC.","tagline":"Pay-per-call premium API access on Base via x402 — $0.02/request in USDC.","description":"This endpoint at lowpaymentfee.com provides \"Premium API Access\" via the x402 payment protocol. The specific path `/api/v1/inbox/144` is one of many endpoints offered by the platform, which advertises a broad catalog spanning data & analytics, AI & machine learning (sentiment analysis, summarization, classification, embeddings), finance & Web3 (price feeds, exchange rates, token quotes, gas estimates), and infrastructure utilities (geocoding, validation, conversion, generation). All endpoints are priced at $0.02 per request, settled in USDC on the Base network.\n\nThe x402 challenge confirms the endpoint is live, accepting POST requests and requiring payment of up to 20,000 base units of USDC (0x8335…2913 on Base). Since USDC uses 6 decimals, this equals $0.02 per call — consistent with the site's advertised pricing. Payment is made via the x402 exact scheme with a 300-second timeout. No API keys or rate limits are required; access is instant once payment is included in the X-PAYMENT header.\n\nNote that the specific functionality behind `/api/v1/inbox/144` is not documented on the landing page — it does not appear in the listed catalog of endpoints. The \"Premium API Access\" description is generic and does not clarify what data or service this particular path returns. The platform's other endpoints are better documented by category, but this one lacks a clear description of its input/output behavior.","tags":[],"capabilities":["x402-payment","usdc-base","pay-per-request","no-api-key","post-endpoint","json-response"],"categories":["api","infrastructure"],"synonyms":["lowpaymentfee","x402 api","pay-per-call api","USDC micropayment api","base network api","premium api access"],"warnings":["The endpoint /api/v1/inbox/144 is not listed in the provider's public API catalog — its specific function is unknown.","No input or output schema is documented; the outputSchema in the challenge only specifies HTTP POST.","The /api, /pricing, and /README pages returned only a 'Connect wallet' prompt with no useful documentation.","Without knowing what this endpoint actually does, integrators cannot predict its behavior."],"endpointUrl":"https://lowpaymentfee.com/api/v1/inbox/144","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/144","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.300","qualityRationale":"The x402 challenge is live and pricing is clear ($0.02 USDC on Base), but the specific endpoint /api/v1/inbox/144 has no documented purpose, no input/output schema, and no examples. It does not appear in the site's listed catalog, making it effectively a stub listing with unknown 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'/request':13,28 '0.02':12,27,95,139 '000':123 '0x8335':128 '20':122 '2913':129 '300':159 '6':135 'USDC micropayment api' 'accept':113 'access':7,22,38,170,210 'advertis':58,147 'ai':65 'analysi':69 'analyt':64 'api':6,21,37,163,209 'appear':200 'base':9,24,103,124,131 'base network api' 'behavior':246 'behind':188 'better':232 'broad':60 'call':4,19,141 'catalog':61,204 'categori':235 'challeng':107 'clarifi':217 'classif':71 'clear':241 'confirm':108 'consist':142 'convers':88 'data':63,219 'decim':136 'descript':211,242 'document':192,233 'embed':72 'endpoint':32,52,91,110,206,230 'equal':138 'estim':82 'exact':155 'exchang':77 'feed':76 'financ':73 'function':187 'gas':81 'generat':89 'generic':213 'geocod':86 'header':182 'includ':176 'infrastructur':84 'input/output':245 'instant':172 'json-response' 'key':164 'lack':239 'land':195 'learn':67 'limit':167 'list':203 'live':112 'lowpaymentfee' 'lowpaymentfee.com':34 'machin':66 'made':151 'mani':51 'network':104 'no-api-key' 'note':183 'offer':53 'one':49,238 'page':196 'particular':223 'path':46,224 'pay':2,17 'pay-per-cal':1,16 'pay-per-call api' 'pay-per-request' 'payment':42,118,149,174,181 'per':3,18,96,140 'platform':56,227 'post':114 'post-endpoint' 'premium':5,20,36,208 'premium api access' 'price':75,93,148 'protocol':43 'provid':35 'quot':80 'rate':78,166 'request':97,115 'requir':117,169 'return':225 'scheme':156 'second':160 'sentiment':68 'servic':221 'settl':98 'sinc':132 'site':145 'span':62 'specif':45,186 'summar':70 'timeout':161 'token':79 'unit':125 'usdc':15,30,100,127,133 'usdc-base' 'use':134 'util':85 'valid':87 'via':10,25,39,152 'web3':74 'x':180 'x-payment':179 'x402':11,26,41,106,154 'x402 api' 'x402-payment'","prices":[{"id":"018cf7ac-70d3-436b-a815-02c74a9df4ac","listingId":"01edf3cb-31a1-48a3-b4fa-a213a260acb6","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/144","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-21T18:32:20.567Z"}],"sources":[{"listingId":"01edf3cb-31a1-48a3-b4fa-a213a260acb6","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/inbox/144","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:20.567Z","lastSeenAt":"2026-04-22T01:02:15.094Z"}],"details":{"listingId":"01edf3cb-31a1-48a3-b4fa-a213a260acb6","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/inbox/144 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <x402-payment-token>\" \\\n  -d '{}'","exampleRequest":null,"exampleResponse":null,"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"All endpoints priced at $0.02 per request with no API keys, no rate limits, instant access on Base network","source_url":"https://lowpaymentfee.com"},{"claim":"x402 challenge returns maxAmountRequired of 20000 base units of USDC (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base, equaling $0.02","source_url":"https://lowpaymentfee.com/api/v1/inbox/144"},{"claim":"Platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories","source_url":"https://lowpaymentfee.com"}],"useCases":["Programmatic access to premium API services with per-request USDC micropayments","Agent-driven workflows that need keyless, pay-as-you-go API access on Base","Testing x402 payment protocol integrations against a live endpoint"],"bestFor":["Developers exploring x402 payment-gated APIs","AI agents needing keyless pay-per-call access","Low-volume consumers who want no subscriptions or commitments"],"notFor":["Users who need detailed documentation of input/output schemas before integrating","High-volume consumers who would benefit from bulk pricing or subscriptions","Anyone without a Base-compatible USDC wallet"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:08.742Z"},"updatedAt":"2026-04-22T01:02:15.094Z"}}