{"id":"3f630230-dd4f-4568-b574-bdc77fd6bba6","shortId":"8yZKBS","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":"This endpoint at lowpaymentfee.com provides \"Premium API Access\" via the x402 payment protocol. The site hosts a broad catalog of pay-per-request APIs spanning data & analytics, AI/ML inference (sentiment analysis, summarization, classification, embeddings), finance & Web3 (price feeds, exchange rates, token quotes, gas estimates), and infrastructure utilities (geocoding, validation, conversion, generation). All endpoints are priced at $0.02 per request, settled in USDC on the Base network.\n\nThe specific endpoint `/api/v1/charges/394` is listed as \"Premium API Access\" and returns a valid x402 challenge with a maxAmountRequired of 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02. Payment is made via the x402 exact scheme — no API keys, no rate limits, and no subscriptions required. The endpoint accepts POST requests and returns application/json.\n\nDocumentation is extremely sparse: the /docs, /pricing, /api, and /README pages all render only a \"Connect wallet\" prompt with no further content. There is no OpenAPI spec, no request/response schema documentation, and no examples of what this particular endpoint actually returns. The site's landing page confirms the pricing model and lists available endpoints, but does not describe the input parameters or output format for any of them. Without knowing what data or functionality `/api/v1/charges/394` specifically provides, agents should treat this as an opaque premium endpoint until more documentation surfaces.","tags":[],"capabilities":["x402-payment","usdc-settlement","base-network","pay-per-request","no-api-key","json-response"],"categories":["api","infrastructure"],"synonyms":["x402 API","pay-per-call API","USDC micropayment API","Base network API","lowpaymentfee","premium API access","crypto-paid API"],"warnings":["No documentation available — /docs, /pricing, /api, and /README pages all show only 'Connect wallet' with no content.","No OpenAPI or schema definition found for any endpoint.","The specific functionality of /api/v1/charges/394 ('Premium API Access') is not described anywhere — unclear what it returns.","No request or response examples are available."],"endpointUrl":"https://lowpaymentfee.com/api/v1/charges/394","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/394","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.300","qualityRationale":"The endpoint is live and returns a valid x402 challenge, confirming pricing and payment details. However, there is no OpenAPI spec, no documentation of request parameters or response schema, and the specific functionality of /api/v1/charges/394 is entirely undocumented. The docs/pricing/README pages are all blank beyond a wallet connect 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'/api/v1/charges/394':101,231 '/docs':162 '/pricing':163 '/readme':166 '/request':13,28 '0.02':12,27,88,130 '000':119 '0x8335':124 '20':118 '2913':125 'Base network API' 'USDC micropayment API' 'accept':151 'access':7,22,38,107 'actual':196 'agent':234 'ai/ml':59 'analysi':62 'analyt':58 'api':6,21,37,55,106,140 'application/json':156 'avail':209 'base':9,24,96,120,127 'base-network' 'broad':48 'call':4,19 'catalog':49 'challeng':113 'classif':64 'confirm':203 'connect':172 'content':178 'convers':81 'crypto-paid API' 'data':57,228 'describ':214 'document':157,187,245 'embed':65 'endpoint':32,84,100,150,195,210,242 'equal':129 'estim':75 'exact':137 'exampl':190 'exchang':70 'extrem':159 'feed':69 'financ':66 'format':220 'function':230 'gas':74 'generat':82 'geocod':79 'host':46 'infer':60 'infrastructur':77 'input':216 'json-response' 'key':141 'know':226 'land':201 'limit':144 'list':103,208 'lowpaymentfee' 'lowpaymentfee.com':34 'made':133 'maxamountrequir':116 'model':206 'network':97 'no-api-key' 'opaqu':240 'openapi':182 'output':219 'page':167,202 'paramet':217 'particular':194 'pay':2,17,52 'pay-per-cal':1,16 'pay-per-call API' 'pay-per-request':51 'payment':42,131 'per':3,18,53,89 'post':152 'premium':5,20,36,105,241 'premium API access' 'price':68,86,205 'prompt':174 'protocol':43 'provid':35,233 'quot':73 'rate':71,143 'render':169 'request':54,90,153 'request/response':185 'requir':148 'return':109,155,197 'schema':186 'scheme':138 'sentiment':61 'settl':91 'site':45,199 'span':56 'spars':160 'spec':183 'specif':99,232 'subscript':147 'summar':63 'surfac':246 'token':72 'treat':236 'unit':121 'usdc':15,30,93,123 'usdc-settlement' 'util':78 'valid':80,111 'via':10,25,39,134 'wallet':173 'web3':67 'without':225 'x402':11,26,41,112,136 'x402 API' 'x402-payment'","prices":[{"id":"9c8c8beb-62bf-4e8f-aa49-242314082677","listingId":"3f630230-dd4f-4568-b574-bdc77fd6bba6","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/394","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:45:26.556Z"}],"sources":[{"listingId":"3f630230-dd4f-4568-b574-bdc77fd6bba6","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/charges/394","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:45:26.556Z","lastSeenAt":"2026-04-22T12:03:43.179Z"}],"details":{"listingId":"3f630230-dd4f-4568-b574-bdc77fd6bba6","quickStartSnippet":"# 1. Send a POST to get the x402 payment challenge\ncurl -X POST https://lowpaymentfee.com/api/v1/charges/394\n# Returns 402 with x402 payment challenge\n# 2. Construct X-PAYMENT header per x402 spec, pay 0.02 USDC on Base\ncurl -X POST https://lowpaymentfee.com/api/v1/charges/394 \\\n  -H \"X-PAYMENT: <signed-payment-token>\"","exampleRequest":null,"exampleResponse":null,"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"All endpoints priced at $0.02 per request with no API keys, no rate limits, settled on Base network","source_url":"https://lowpaymentfee.com"},{"claim":"x402 challenge returns maxAmountRequired of 20000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base","source_url":"https://lowpaymentfee.com/api/v1/charges/394"},{"claim":"Site lists APIs across data & analytics, AI/ML, finance & Web3, and infrastructure categories","source_url":"https://lowpaymentfee.com"}],"useCases":["Accessing premium API functionality with per-request USDC micropayments on Base","Agent-driven API consumption without API key management","Pay-as-you-go data or service access settled on-chain"],"bestFor":["Agents or applications that need keyless, on-demand API access","Users who prefer crypto micropayments over subscription billing","Developers experimenting with x402 protocol integrations"],"notFor":["Users who need detailed API documentation or guaranteed SLAs before purchasing","High-volume consumers who would benefit from bulk pricing or subscriptions","Anyone unable to transact in USDC on the Base network"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:21.556Z"},"updatedAt":"2026-04-22T12:03:43.179Z"}}