{"id":"a09a8300-5df0-4b16-ac66-6e0d946f5375","shortId":"khwzSu","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/21` is labeled \"Premium API Access\" and requires a USDC payment on Base (asset 0x8335…2913) of up to 20,000 base units (i.e., $0.02 given USDC's 6 decimals) per call. No API keys, rate limits, or upfront commitments are needed — 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 are listed at $0.02 per request.\n\nHowever, the specific `/api/v1/charges/21` endpoint's actual functionality is not documented beyond the label \"Premium API Access.\" The crawled docs, pricing, and README pages all returned only a \"Connect wallet\" prompt with no further technical documentation, request/response schemas, or usage examples. Without knowing what this endpoint actually returns, callers should treat it as an opaque premium resource until more documentation surfaces.","tags":[],"capabilities":["x402-payment","usdc-base","pay-per-request","no-api-key","no-rate-limit","json-response"],"categories":["api-gateway","payments"],"synonyms":["x402 API","pay-per-call API","USDC micropayment API","Base network API","lowpaymentfee","premium API access","crypto-paid endpoint"],"warnings":["No documentation available — docs, pricing, and README pages all return only 'Connect wallet' with no content.","The actual functionality behind 'Premium API Access' at /api/v1/charges/21 is completely undocumented.","No request or response schema is provided; callers cannot know what to send or what to expect back.","No OpenAPI spec, ai-plugin manifest, or agents.txt discovered."],"endpointUrl":"https://lowpaymentfee.com/api/v1/charges/21","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/21","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 captured) and pricing is clear ($0.02 USDC on Base), but there is zero documentation on what the endpoint actually does, no request/response schema, and no examples. The docs, pricing, and README pages are all empty beyond a wallet-connect prompt. This is effectively a stub 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'/request':13,28 '0.02':12,27,80,158 '000':76 '0x8335':70 '20':75 '2913':71 '6':84 'Base network API' 'USDC micropayment API' 'access':7,22,42,61,177 'across':118 'actual':167,207 'advertis':116 'ai':128 'analysi':132 'analyt':122 'api':6,21,40,60,89,176 'asset':69 'attach':100 'base':9,24,50,68,77 'beyond':172 'broader':113 'call':4,19,87 'caller':98,209 'categori':120 'classif':135 'collect':34 'commit':95 'connect':189 'convers':152 'crawl':179 'crypto-paid endpoint' 'data':121,125 'decim':85 'doc':180 'document':171,196,220 'embed':136 'endpoint':41,54,117,165,206 'estim':146 'exampl':201 'exchang':141 'export':126 'feed':140 'financ':137 'four':119 'function':168 'gas':145 'generat':153 'geocod':150 'given':81 'header':105 'host':32 'howev':161 'i.e':79 'infrastructur':148 'insight':127 'json-response' 'key':90 'know':203 'label':58,174 'learn':130 'limit':92 'list':156 'lowpaymentfee' 'lowpaymentfee.com':31,114 'machin':129 'metric':123 'need':97 'network':51 'no-api-key' 'no-rate-limit' 'opaqu':215 'page':184 'pay':2,17,37 'pay-per-cal':1,16 'pay-per-call API' 'pay-per-request':36 'payment':46,66,104,110 'per':3,18,38,86,159 'platform':115 'premium':5,20,59,175,216 'premium API access' 'price':139,181 'prompt':191 'proof':111 'protocol':47 'quot':144 'rate':91,142 'readm':183 'report':124 'request':39,160 'request/response':197 'requir':63 'resourc':217 'return':186,208 'schema':198 'sentiment':131 'simpli':99 'specif':53,163 'summar':134 'surfac':221 'technic':195 'text':133 'token':143 'treat':211 'unit':78 'upfront':94 'usag':200 'usdc':15,30,65,82 'usdc-base' 'util':149 'valid':108,151 'via':10,25,43 'wallet':190 'web3':138 'without':202 'x':103 'x-payment':102 'x402':11,26,45,109 'x402 API' 'x402-payment'","prices":[{"id":"514d22f1-47c4-47d0-aed3-ed605ba262ca","listingId":"a09a8300-5df0-4b16-ac66-6e0d946f5375","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/21","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:44:37.496Z"}],"sources":[{"listingId":"a09a8300-5df0-4b16-ac66-6e0d946f5375","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/charges/21","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:44:37.496Z","lastSeenAt":"2026-04-24T02:32:12.390Z"}],"details":{"listingId":"a09a8300-5df0-4b16-ac66-6e0d946f5375","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/charges/21 \\\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 challenge requiring up to 20,000 base units of USDC on Base","source_url":"https://lowpaymentfee.com/api/v1/charges/21"},{"claim":"USDC asset address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base","source_url":"https://lowpaymentfee.com/api/v1/charges/21"},{"claim":"Platform advertises $0.02/request pricing with no API keys, no rate limits, and instant access","source_url":"https://lowpaymentfee.com"},{"claim":"Platform lists endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories","source_url":"https://lowpaymentfee.com"},{"claim":"Docs, pricing, and README pages contain only 'Connect wallet' with no further content","source_url":"https://lowpaymentfee.com/docs"}],"useCases":["Programmatic access to a premium resource without API key management","Agent-driven pay-per-call workflows settled in USDC on Base","Testing x402 payment protocol integrations against a live endpoint"],"bestFor":["Developers experimenting with x402 payment flows","AI agents that need keyless, pay-as-you-go API access","Users who want to avoid subscription commitments for occasional API calls"],"notFor":["Users who need detailed API documentation or guaranteed SLAs","High-volume consumers who would benefit from bulk pricing or subscriptions","Anyone without a Base-compatible USDC wallet"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:23.844Z"},"updatedAt":"2026-04-24T02:32:12.390Z"}}