{"id":"a6b8e4d1-27db-4fa2-a506-deee7f57ee3a","shortId":"b6PV6S","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 provides a broad catalog of pay-per-request endpoints settled in USDC on the Base network. The specific endpoint at `/api/v1/inbox/28` 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, accounts, or subscriptions are required; callers attach an X-PAYMENT header with a signed USDC payment to each request.\n\nThe wider platform advertises four endpoint 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 listed endpoints share the same $0.02/request pricing. The platform claims no rate limits and no minimum commitments.\n\nImportant caveat: the specific `/api/v1/inbox/28` endpoint's description is simply \"Premium API Access\" with no further documentation about what it actually returns. There is no OpenAPI schema, no example request/response payloads, and no detailed documentation available from the crawled pages. The endpoint is confirmed live (returns a valid 402 x402 challenge), but its actual functionality behind the paywall is unknown.","tags":[],"capabilities":["x402-payment","usdc-base-network","pay-per-request","no-api-key","http-post"],"categories":["api-platform","infrastructure"],"synonyms":["low payment fee","x402 api","pay per call api","usdc api","base network api","micropayment api","premium api access"],"warnings":["No documentation exists for what /api/v1/inbox/28 actually returns — 'Premium API Access' is the only description","No OpenAPI schema or example request/response available","Crawled /api, /pricing, and /README pages returned only 'Connect wallet' with no useful content","The specific functionality behind this endpoint is completely unknown without paying"],"endpointUrl":"https://lowpaymentfee.com/api/v1/inbox/28","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/28","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.300","qualityRationale":"The endpoint is confirmed live with a valid x402 402 challenge, but there is zero documentation on what /api/v1/inbox/28 actually does or returns. No OpenAPI spec, no example payloads, and the crawled pages beyond the homepage are empty wallet-connect stubs. The listing is effectively a stub with only pricing and protocol details 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'/request':19,38,169 '0.02':18,37,80,168 '000':84 '20':83 '402':229 '6':90 'access':75,193 'account':102 'actual':201,234 'advertis':125 'ai':12,31,136 'analysi':140 'analyt':130 'api':5,24,45,74,100,192 'attach':108 'avail':216 'base':8,27,63,85 'base network api' 'behind':236 'broad':50 'call':4,23,82 'caller':107 'catalog':51 'categori':128 'caveat':182 'challeng':231 'claim':173 'classif':143 'commit':180 'confirm':224 'convers':160 'cost':77 'crawl':219 'data':11,30,129,133 'decim':91 'descript':188 'detail':214 'document':197,215 'embed':144 'enabl':44 'endpoint':16,35,57,67,127,164,186,222 'estim':154 'exampl':209 'exchang':149 'export':134 'feed':148 'financ':13,32,145 'four':126 'function':235 'gas':153 'generat':161 'geocod':158 'handl':94 'header':113 'http-post' 'import':181 'infrastructur':156 'insight':135 'key':101 'learn':138 'limit':176 'list':71,163 'live':225 'low payment fee' 'lowpaymentfee.com':39 'machin':137 'metric':131 'micropayment api' 'minimum':179 'network':64 'no-api-key' 'offer':10,29 'openapi':206 'page':220 'pay':2,21,54 'pay per call api' 'pay-per-cal':1,20 'pay-per-request':53 'payload':211 'payment':92,112,118 'paywal':238 'per':3,22,55,81 'platform':6,25,46,124,172 'premium':73,191 'premium api access' 'price':147,170 'protocol':98 'provid':48 'quot':152 'rate':150,175 'report':132 'request':56,121 'request/response':210 'requir':106 'return':202,226 'schema':207 'sentiment':139 'settl':58 'share':165 'sign':116 'simpli':190 'specif':66,184 'subscript':104 'summar':142 'text':141 'token':151 'unit':86 'unknown':240 'usdc':9,28,60,88,117 'usdc api' 'usdc-base-network' 'util':15,34,157 'valid':159,228 'via':95 'web3':146 'wider':123 'x':111 'x-payment':110 'x402':43,97,230 'x402 api' 'x402-enabled':42 'x402-payment'","prices":[{"id":"f216f94e-8bf9-40ef-b3ab-f1b480aa51cb","listingId":"a6b8e4d1-27db-4fa2-a506-deee7f57ee3a","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/28","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-21T18:32:21.888Z"}],"sources":[{"listingId":"a6b8e4d1-27db-4fa2-a506-deee7f57ee3a","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/inbox/28","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:21.888Z","lastSeenAt":"2026-04-22T11:32:57.706Z"}],"details":{"listingId":"a6b8e4d1-27db-4fa2-a506-deee7f57ee3a","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/inbox/28 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <signed-x402-payment-header>\"","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/28"},{"claim":"All listed endpoints are priced at $0.02 per request with no API keys, no rate limits, and no minimums","source_url":"https://lowpaymentfee.com"},{"claim":"The platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/inbox/28"}],"useCases":["Agents needing on-demand API access without managing API keys or subscriptions","Programmatic access to utility or data endpoints with per-call USDC micropayments","Testing x402 protocol integrations against a live endpoint"],"bestFor":["Developers experimenting with x402 payment protocol","Agents that need keyless, pay-as-you-go API access on Base","Low-volume or sporadic API consumers who want no commitments"],"notFor":["Users who need detailed API documentation or guaranteed SLAs before paying","High-volume consumers who would benefit from bulk pricing or subscriptions","Anyone without USDC on the Base network"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:08.247Z"},"updatedAt":"2026-04-22T11:32:57.706Z"}}