{"id":"2b88fd3f-df4d-4699-be54-a15e9c34515b","shortId":"aeksVR","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":"lowpaymentfee.com hosts a collection of pay-per-request API endpoints accessible via the x402 payment protocol on the Base network. The specific endpoint at `/api/v1/charges/4` is labeled \"Premium API Access\" and accepts POST requests. Payment is settled in USDC (contract 0x8335…2913 on Base) with a maximum amount of 20,000 base units, which equals $0.02 per request (USDC uses 6 decimals). No API keys, rate limits, or upfront commitments are required — callers simply attach an X-PAYMENT header with a valid x402 payment proof.\n\nThe broader lowpaymentfee.com platform advertises 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 listed at the same $0.02/request price point.\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 crawled material. The endpoint is confirmed live (returns a proper 402 x402 challenge), but without documentation it is unclear what request body the `/api/v1/charges/4` endpoint expects or what response payload it returns.","tags":[],"capabilities":["x402-payment","usdc-settlement","base-network","pay-per-request","no-api-key","post-endpoint"],"categories":["api-gateway","infrastructure"],"synonyms":["x402 API","pay-per-call API","USDC micropayment API","Base network API","lowpaymentfee","premium API access","crypto-paid API"],"warnings":["No OpenAPI or schema documentation available — request body and response format are unknown","All documentation pages (/docs, /api, /pricing, /README) render only 'Connect wallet' with no technical content","The specific purpose of /api/v1/charges/4 ('Premium API Access') is not explained anywhere in the crawled material","Cannot verify what data or service is actually returned after payment"],"endpointUrl":"https://lowpaymentfee.com/api/v1/charges/4","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/charges/4","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 402 x402 challenge and clear pricing ($0.02 USDC on Base). However, there is no OpenAPI spec, no request/response schema, no documentation beyond a wallet-connect prompt, and no examples. The purpose of this specific '/charges/4' endpoint is entirely opaque beyond its 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'/api/v1/charges/4':56,233 '/docs':176 '/pricing':178 '/readme':180 '/request':13,28,168 '0.02':12,27,87,167 '000':82 '0x8335':72 '20':81 '2913':73 '402':220 '6':92 'Base network API' 'USDC micropayment API' 'accept':63 'access':7,22,42,61 'across':124 'advertis':122 'ai':134 'amount':79 'analysi':138 'analyt':128 'api':6,21,40,60,95 'attach':106 'avail':207 'base':9,24,50,75,83 'base-network' 'bodi':231 'broader':119 'call':4,19 'caller':104 'categori':126 'challeng':222 'classif':141 'collect':34 'commit':101 'confirm':215 'connect':186 'contract':71 'convers':158 'crawl':210 'crypto-paid API' 'data':127,131 'decim':93 'detail':193 'document':171,202,225 'embed':142 'endpoint':41,54,123,161,213,234 'equal':86 'estim':152 'exampl':206 'exchang':147 'expect':235 'export':132 'extrem':173 'feed':146 'financ':143 'four':125 'gas':151 'generat':159 'geocod':156 'header':111 'host':32 'infrastructur':154 'insight':133 'key':96 'label':58 'learn':136 'limit':98 'list':163 'live':216 'lowpaymentfee' 'lowpaymentfee.com':31,120 'machin':135 'materi':211 'maximum':78 'metric':129 'network':51 'no-api-key' 'openapi':197 'page':181 'pay':2,17,37 'pay-per-cal':1,16 'pay-per-call API' 'pay-per-request':36 'payload':239 'payment':46,66,110,116 'per':3,18,38,88 'platform':121 'point':170 'post':64 'post-endpoint' 'premium':5,20,59 'premium API access' 'price':145,169 'prompt':188 'proof':117 'proper':219 'protocol':47 'quot':150 'rate':97,148 'render':183 'report':130 'request':39,65,89,230 'request/response':200 'requir':103 'respons':238 'return':217,241 'schema':201 'sentiment':137 'settl':68 'simpli':105 'spars':174 'spec':198 'specif':53 'summar':140 'technic':192 'text':139 'token':149 'unclear':228 'unit':84 'upfront':100 'usag':205 'usdc':15,30,70,90 'usdc-settlement' 'use':91 'util':155 'valid':114,157 'via':10,25,43 'wallet':187 'web3':144 'without':224 'x':109 'x-payment':108 'x402':11,26,45,115,221 'x402 API' 'x402-payment'","prices":[{"id":"d2a38672-b6e0-4a28-8d1a-94f243761b2d","listingId":"2b88fd3f-df4d-4699-be54-a15e9c34515b","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/charges/4","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:45:27.797Z"}],"sources":[{"listingId":"2b88fd3f-df4d-4699-be54-a15e9c34515b","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/charges/4","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:45:27.797Z","lastSeenAt":"2026-04-23T23:02:31.636Z"}],"details":{"listingId":"2b88fd3f-df4d-4699-be54-a15e9c34515b","quickStartSnippet":"# The endpoint returns 402 with an x402 challenge.\n# Attach a valid X-PAYMENT header (x402 v1, USDC on Base) to pay $0.02.\ncurl -X POST https://lowpaymentfee.com/api/v1/charges/4 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <x402-payment-proof>\"","exampleRequest":null,"exampleResponse":null,"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"Endpoint returns 402 with x402 v1 challenge accepting USDC on Base network with maxAmountRequired of 20000 base units","source_url":"https://lowpaymentfee.com/api/v1/charges/4"},{"claim":"USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base","source_url":"https://lowpaymentfee.com/api/v1/charges/4"},{"claim":"Platform advertises $0.02/request pricing with no API keys, no rate limits, and instant access","source_url":"https://lowpaymentfee.com"},{"claim":"Available API categories include Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructure","source_url":"https://lowpaymentfee.com"}],"useCases":["Accessing premium API functionality with per-request USDC micropayments on Base","Agent-driven API consumption without pre-registration or API key management","Programmatic pay-as-you-go access to data, AI, finance, or utility endpoints"],"bestFor":["Developers wanting zero-signup, pay-per-call API access","AI agents that can settle x402 payments autonomously on Base","Users who prefer crypto micropayments over subscription billing"],"notFor":["Users needing detailed API documentation or OpenAPI specs before integrating","High-volume consumers who need bulk pricing or rate-limit guarantees","Developers who cannot transact in USDC on the Base network"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:21.467Z"},"updatedAt":"2026-04-23T23:02:31.636Z"}}