{"id":"340b2f6b-ff81-4e8c-8bab-8986af9c1231","shortId":"N8bGUs","kind":"x402","title":"Pay-per-call API platform on Base network via x402 — $0.02/request in USDC.","tagline":"Pay-per-call API platform on Base network via x402 — $0.02/request in USDC.","description":"lowpaymentfee.com is an x402-enabled API platform that offers a broad set of endpoints spanning data analytics, AI/ML inference, finance/Web3 data, and utility services. Every endpoint costs $0.02 per request, paid in USDC on the Base network with no API keys, no rate limits, and no commitments required. The specific endpoint at `/api/v1/transactions/121` is listed as \"Premium API Access\" and returns a 402 challenge requesting up to 20,000 base units of USDC (i.e., $0.02) per call.\n\nThe platform advertises four categories of APIs: 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 appear to follow the same x402 payment flow — POST with an X-PAYMENT header containing a signed payment proof settled on Base.\n\nDocumentation is extremely sparse. The /docs, /api, /pricing, and /README pages all render only a \"Connect wallet\" prompt with no further technical detail. There is no OpenAPI spec, no request/response schema documentation, and no usage examples available from the crawl. The endpoint is confirmed live (402 challenge captured), but without documentation it is unclear what request body the `/api/v1/transactions/121` endpoint expects or what response it returns.","tags":[],"capabilities":["x402-payment","usdc-base-network","pay-per-request","data-analytics","ai-sentiment","ai-summarization","ai-classification","ai-embeddings","finance-price-feeds","exchange-rates","crypto-gas-estimates","geocoding","validation","conversion"],"categories":["api-platform","ai","finance","infrastructure"],"synonyms":["low payment fee","x402 api","pay per call api","usdc api","base network api","micropayment api","crypto api gateway"],"warnings":["No API documentation available — /docs, /api, /pricing, and /README pages all show only 'Connect wallet' with no technical content","No OpenAPI or schema definition found for any endpoint","The purpose and expected input/output of /api/v1/transactions/121 is unclear — 'Premium API Access' is not descriptive","Cannot verify that the advertised AI, finance, and utility endpoints actually function as described"],"endpointUrl":"https://lowpaymentfee.com/api/v1/transactions/121","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/transactions/121","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.350","qualityRationale":"The endpoint is confirmed live with a valid 402 challenge and clear pricing ($0.02 USDC on Base). However, documentation is essentially nonexistent — no OpenAPI spec, no request/response schemas, no examples. The specific purpose of /api/v1/transactions/121 ('Premium API Access') is vague and 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'/api/v1/transactions/121':84,232 '/docs':179 '/pricing':181 '/readme':183 '/request':13,28 '0.02':12,27,59,106 '000':100 '20':99 '402':94,219 'access':90 'advertis':111 'ai':123 'ai-classification' 'ai-embeddings' 'ai-sentiment' 'ai-summarization' 'ai/ml':49 'analysi':127 'analyt':48,117 'api':5,20,37,71,89,115 'appear':151 'avail':210 'base':8,23,67,101,173 'base network api' 'bodi':230 'broad':42 'call':4,19,108 'captur':221 'categori':113 'challeng':95,220 'classif':130 'commit':78 'confirm':217 'connect':189 'contain':166 'convers':147 'conversion' 'cost':58 'crawl':213 'crypto api gateway' 'crypto-gas-estimates' 'data':47,52,116,120 'data-analytics' 'detail':196 'document':174,205,224 'embed':131 'enabl':36 'endpoint':45,57,82,150,215,233 'estim':141 'everi':56 'exampl':209 'exchang':136 'exchange-rates' 'expect':234 'export':121 'extrem':176 'feed':135 'financ':132 'finance-price-feeds' 'finance/web3':51 'flow':158 'follow':153 'four':112 'gas':140 'generat':148 'geocod':145 'geocoding' 'header':165 'i.e':105 'infer':50 'infrastructur':143 'insight':122 'key':72 'learn':125 'limit':75 'list':86 'live':218 'low payment fee' 'lowpaymentfee.com':31 'machin':124 'metric':118 'micropayment api' 'network':9,24,68 'offer':40 'openapi':200 'page':184 'paid':62 'pay':2,17 'pay per call api' 'pay-per-cal':1,16 'pay-per-request' 'payment':157,164,169 'per':3,18,60,107 'platform':6,21,38,110 'post':159 'premium':88 'price':134 'prompt':191 'proof':170 'quot':139 'rate':74,137 'render':186 'report':119 'request':61,96,229 'request/response':203 'requir':79 'respons':237 'return':92,239 'schema':204 'sentiment':126 'servic':55 'set':43 'settl':171 'sign':168 'span':46 'spars':177 'spec':201 'specif':81 'summar':129 'technic':195 'text':128 'token':138 'unclear':227 'unit':102 'usag':208 'usdc':15,30,64,104 'usdc api' 'usdc-base-network' 'util':54,144 'valid':146 'validation' 'via':10,25 'wallet':190 'web3':133 'without':223 'x':163 'x-payment':162 'x402':11,26,35,156 'x402 api' 'x402-enabled':34 'x402-payment'","prices":[{"id":"716396d2-b663-4257-9e66-ecc191e037a7","listingId":"340b2f6b-ff81-4e8c-8bab-8986af9c1231","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/transactions/121","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:58:24.398Z"}],"sources":[{"listingId":"340b2f6b-ff81-4e8c-8bab-8986af9c1231","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/transactions/121","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:58:24.398Z","lastSeenAt":"2026-04-22T13:31:44.523Z"}],"details":{"listingId":"340b2f6b-ff81-4e8c-8bab-8986af9c1231","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/transactions/121 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <signed-x402-payment-proof>\" \\\n  -d '{}'","exampleRequest":null,"exampleResponse":null,"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"All endpoints cost $0.02 per request with no API keys, no rate limits, and instant access on Base network","source_url":"https://lowpaymentfee.com"},{"claim":"The platform offers Data & Analytics, AI & ML, Finance & Web3, and Infrastructure API categories","source_url":"https://lowpaymentfee.com"},{"claim":"The /api/v1/transactions/121 endpoint returns a 402 challenge requesting up to 20,000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base","source_url":"https://lowpaymentfee.com/api/v1/transactions/121"}],"useCases":["Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without API key management","Fetching real-time financial data like token prices, exchange rates, and gas estimates on a per-call basis","Running utility operations such as geocoding, validation, and data conversion with micropayments"],"bestFor":["Developers wanting zero-commitment, pay-as-you-go API access via crypto","Agents that can settle x402 payments in USDC on Base","Projects needing lightweight access to multiple API categories without subscription overhead"],"notFor":["Users who need detailed API documentation or OpenAPI specs before integrating","High-volume consumers who would benefit from bulk pricing or rate-limited plans","Teams that cannot transact in USDC on the Base network"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:44.155Z"},"updatedAt":"2026-04-22T13:31:44.523Z"}}