{"id":"e607023e-71f4-4f56-a642-54bc16ba20f4","shortId":"k3gtnN","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 hosts a broad catalog of pay-per-request endpoints across four categories: 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 priced at $0.02 per request, settled in USDC on the Base network via the x402 protocol.\n\nThe specific endpoint `/api/v1/inbox/15` is listed as \"Premium API Access.\" Its x402 challenge advertises a maxAmountRequired of 20,000 base units of USDC (0x8335… on Base), which equals $0.02 given USDC's 6 decimals. Payment is made via the x402 exact scheme with no API keys, no rate limits, and no subscriptions required — callers simply attach an X-PAYMENT header to each POST request.\n\nDocumentation is minimal: the site's landing page lists available endpoints and pricing, but the /api, /pricing, and /README pages all resolve to a wallet-connect prompt with no further content. There is no OpenAPI spec, no request/response schema documentation, and no usage examples. The purpose of the `/api/v1/inbox/15` endpoint specifically is unclear — it does not appear in the site's public catalog, so its functionality cannot be confirmed from available materials.","tags":[],"capabilities":["x402-payment","usdc-base","pay-per-request","post-endpoint","no-api-key","no-rate-limit"],"categories":["api-platform","infrastructure"],"synonyms":["low payment fee","x402 api","micropayment api","pay per call api","base usdc api","lowpaymentfee"],"warnings":["The endpoint /api/v1/inbox/15 does not appear in the site's public API catalog; its purpose is undocumented.","No OpenAPI spec, no request/response schema, and no usage examples are available.","The /api, /pricing, and /README pages only show a wallet-connect prompt with no documentation content.","Actual functionality behind this endpoint cannot be verified from available materials."],"endpointUrl":"https://lowpaymentfee.com/api/v1/inbox/15","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/15","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.300","qualityRationale":"The endpoint is live (402 challenge confirmed) and pricing is clear ($0.02 USDC on Base), but there is no OpenAPI spec, no request/response schema, no documentation beyond a landing page catalog, and the specific /api/v1/inbox/15 endpoint is not listed in the public catalog — its actual functionality is 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'/api/v1/inbox/15':116,227 '/pricing':194 '/readme':196 '/request':19,38 '0.02':18,37,99,141 '000':131 '0x8335':136 '20':130 '6':145 'access':122 'across':58 'advertis':126 'ai':12,31,68 'analysi':72 'analyt':62 'api':5,24,45,121,157 'appear':235 'attach':168 'avail':187,249 'base':8,27,107,132,138 'base usdc api' 'broad':50 'call':4,23 'caller':166 'cannot':245 'catalog':51,241 'categori':60 'challeng':125 'classif':75 'confirm':247 'connect':204 'content':209 'convers':92 'data':11,30,61,65 'decim':146 'document':178,218 'embed':76 'enabl':44 'endpoint':16,35,57,95,115,188,228 'equal':140 'estim':86 'exact':153 'exampl':222 'exchang':81 'export':66 'feed':80 'financ':13,32,77 'four':59 'function':244 'gas':85 'generat':93 'geocod':90 'given':142 'header':173 'host':48 'infrastructur':88 'insight':67 'key':158 'land':184 'learn':70 'limit':161 'list':118,186 'low payment fee' 'lowpaymentfee' 'lowpaymentfee.com':39 'machin':69 'made':149 'materi':250 'maxamountrequir':128 'metric':63 'micropayment api' 'minim':180 'network':108 'no-api-key' 'no-rate-limit' 'offer':10,29 'openapi':213 'page':185,197 'pay':2,21,54 'pay per call api' 'pay-per-cal':1,20 'pay-per-request':53 'payment':147,172 'per':3,22,55,100 'platform':6,25,46 'post':176 'post-endpoint' 'premium':120 'price':79,97,190 'prompt':205 'protocol':112 'public':240 'purpos':224 'quot':84 'rate':82,160 'report':64 'request':56,101,177 'request/response':216 'requir':165 'resolv':199 'schema':217 'scheme':154 'sentiment':71 'settl':102 'simpli':167 'site':182,238 'spec':214 'specif':114,229 'subscript':164 'summar':74 'text':73 'token':83 'unclear':231 'unit':133 'usag':221 'usdc':9,28,104,135,143 'usdc-base' 'util':15,34,89 'valid':91 'via':109,150 'wallet':203 'wallet-connect':202 'web3':78 'x':171 'x-payment':170 'x402':43,111,124,152 'x402 api' 'x402-enabled':42 'x402-payment'","prices":[{"id":"01e17ae4-c3e5-4c35-8339-b186dd9309b3","listingId":"e607023e-71f4-4f56-a642-54bc16ba20f4","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/15","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-21T18:32:20.538Z"}],"sources":[{"listingId":"e607023e-71f4-4f56-a642-54bc16ba20f4","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/inbox/15","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:20.538Z","lastSeenAt":"2026-04-22T13:32:22.465Z"}],"details":{"listingId":"e607023e-71f4-4f56-a642-54bc16ba20f4","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/inbox/15 \\\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 are priced at $0.02 per request with no API keys, no rate limits, and instant access on the Base network.","source_url":"https://lowpaymentfee.com"},{"claim":"The x402 challenge for /api/v1/inbox/15 advertises maxAmountRequired of 20000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base.","source_url":"https://lowpaymentfee.com/api/v1/inbox/15"},{"claim":"Available API categories include Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructure.","source_url":"https://lowpaymentfee.com"}],"useCases":["Accessing pay-per-call API services without subscriptions or API keys","Making micropayment-gated HTTP requests settled on Base L2 in USDC","Integrating agent-purchasable endpoints into automated workflows"],"bestFor":["Developers wanting zero-commitment, pay-as-you-go API access","AI agents that can settle x402 payments autonomously on Base","Projects needing low-cost per-request pricing without rate limits"],"notFor":["Users who need detailed API documentation or OpenAPI specs before integrating","High-volume consumers who would benefit from bulk/subscription pricing","Anyone unable to pay in USDC on the Base network"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:08.871Z"},"updatedAt":"2026-04-22T13:32:22.465Z"}}