{"id":"398416ec-88f3-43b5-87a8-7104b9a97433","shortId":"tSBb6b","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 collection of endpoints spanning data analytics, AI/ML inference, finance/Web3 data, and general utility services. Every endpoint is priced at $0.02 per request, settled in USDC on the Base network via the x402 payment protocol. There are no API keys, no rate limits, and no minimum commitments — callers simply attach an X-PAYMENT header with a valid payment proof to each request.\n\nThe specific endpoint at `/api/v1/keys/16` is listed as \"Premium API Access\" and returns a 402 challenge requesting up to 20,000 base units of USDC (i.e., $0.02) on Base. The 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 pricing and payment model.\n\nDocumentation is minimal — the site's /api, /pricing, and /README pages all resolve to a \"Connect wallet\" prompt with no further detail. There is no OpenAPI spec, no request/response schema documentation, and no usage examples available from the crawled material. The endpoint is confirmed live (402 challenge captured), but the lack of documentation makes it difficult to know what request bodies are expected or what response payloads look like.","tags":[],"capabilities":["x402-payment","per-request-pricing","usdc-base-settlement","data-analytics","ai-sentiment","ai-summarization","ai-classification","ai-embeddings","finance-price-feeds","exchange-rates","crypto-gas-estimates","geocoding","validation","conversion"],"categories":["ai","finance","data","utility"],"synonyms":["pay-per-call API","micropayment API","x402 API","USDC API","Base network API","low fee API","crypto-paid API","serverless API"],"warnings":["No OpenAPI or schema documentation available — request/response formats are unknown","The /api, /pricing, and /README pages all return only a 'Connect wallet' prompt with no useful content","The purpose of /api/v1/keys/16 ('Premium API Access') is ambiguous — it may differ from the other listed endpoints","No examples or error documentation found"],"endpointUrl":"https://lowpaymentfee.com/api/v1/keys/16","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/keys/16","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, there is no OpenAPI spec, no request/response schema, no documentation beyond a landing page listing endpoint names, and no examples. The purpose of this specific endpoint (/api/v1/keys/16 labeled 'Premium API Access') is unclear — it may be a meta-endpoint for key generation rather than a data API. Significant uncertainty 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'/api/v1/keys/16':117 '/pricing':199 '/readme':201 '/request':19,38 '0.02':18,37,70,139 '000':133 '20':132 '402':127,237 'Base network API' 'USDC API' 'access':123 'advertis':144 'ai':12,31,156 'ai-classification' 'ai-embeddings' 'ai-sentiment' 'ai-summarization' 'ai/ml':57 'analysi':160 'analyt':56,150 'api':5,24,45,88,122,148 'appear':183 'attach':99 'avail':227 'base':8,27,78,134,141 'bodi':252 'broad':50 'call':4,23 'caller':97 'captur':239 'categori':146 'challeng':128,238 'classif':163 'collect':51 'commit':96 'confirm':235 'connect':207 'convers':179 'conversion' 'crawl':230 'crypto-gas-estimates' 'crypto-paid API' 'data':11,30,55,60,149,153 'data-analytics' 'detail':213 'difficult':247 'document':192,222,244 'embed':164 'enabl':44 'endpoint':16,35,53,66,115,182,233 'estim':174 'everi':65 'exampl':226 'exchang':169 'exchange-rates' 'expect':254 'export':154 'feed':168 'financ':13,32,165 'finance-price-feeds' 'finance/web3':59 'follow':185 'four':145 'gas':173 'general':62 'generat':180 'geocod':177 'geocoding' 'header':104 'i.e':138 'infer':58 'infrastructure/utilities':176 'insight':155 'key':89 'know':249 'lack':242 'learn':158 'like':260 'limit':92 'list':119 'live':236 'look':259 'low fee API' 'lowpaymentfee.com':39 'machin':157 'make':245 'materi':231 'metric':151 'micropayment API' 'minim':194 'minimum':95 'model':191 'network':79 'offer':10,29 'openapi':217 'page':202 'pay':2,21 'pay-per-cal':1,20 'pay-per-call API' 'payload':258 'payment':83,103,108,190 'per':3,22,71 'per-request-pricing' 'platform':6,25,46,143 'premium':121 'price':68,167,188 'prompt':209 'proof':109 'protocol':84 'provid':48 'quot':172 'rate':91,170 'report':152 'request':72,112,129,251 'request/response':220 'resolv':204 'respons':257 'return':125 'schema':221 'sentiment':159 'serverless API' 'servic':64 'settl':73 'simpli':98 'site':196 'span':54 'spec':218 'specif':114 'summar':162 'text':161 'token':171 'unit':135 'usag':225 'usdc':9,28,75,137 'usdc-base-settlement' 'util':15,34,63 'valid':107,178 'validation' 'via':80 'wallet':208 'web3':166 'x':102 'x-payment':101 'x402':43,82 'x402 API' 'x402-enabled':42 'x402-payment'","prices":[{"id":"38e17388-d41e-452d-8ab8-7a70b8bdc115","listingId":"398416ec-88f3-43b5-87a8-7104b9a97433","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/keys/16","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-21T18:32:23.165Z"}],"sources":[{"listingId":"398416ec-88f3-43b5-87a8-7104b9a97433","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/keys/16","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:23.165Z","lastSeenAt":"2026-04-22T01:02:18.351Z"}],"details":{"listingId":"398416ec-88f3-43b5-87a8-7104b9a97433","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/keys/16 \\\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 402 challenge requesting up to 20,000 base units of USDC ($0.02) on Base network","source_url":"https://lowpaymentfee.com/api/v1/keys/16"},{"claim":"The platform lists endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories, all priced at $0.02/request","source_url":"https://lowpaymentfee.com"},{"claim":"The platform advertises no API keys, no rate limits, and instant access","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset contract on Base: 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/keys/16"}],"useCases":["Agents that need on-demand AI inference (sentiment, summarization, classification, embeddings) without managing API keys","Fetching real-time crypto price feeds, gas estimates, or exchange rates with per-call payment","Running data analytics queries or exporting data with no subscription commitment","Geocoding, validation, or format conversion as utility microservices"],"bestFor":["AI agents and bots that can settle payments via x402 on Base","Developers wanting zero-commitment, pay-as-you-go API access","Use cases requiring low-cost ($0.02) per-request pricing without rate limits"],"notFor":["Users who need detailed API documentation or OpenAPI specs before integrating","High-volume production workloads where subscription pricing would be cheaper","Callers who cannot transact in USDC on the Base network"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:06.189Z"},"updatedAt":"2026-04-22T01:02:18.351Z"}}