{"id":"9153ce6f-d1d5-437d-81e3-2cef95cc866b","shortId":"W9spqj","kind":"x402","title":"x402-gated API suite on Base: analytics, AI, finance, and utility endpoints at $0.02/request.","tagline":"x402-gated API suite on Base: analytics, AI, finance, and utility endpoints at $0.02/request.","description":"lowpaymentfee.com offers a collection of pay-per-call API endpoints gated by the x402 protocol, settling payments in USDC on the Base network. The specific endpoint `/api/v1/cards/20` is listed as \"Premium API Access\" and costs $0.02 per request (20,000 base units of USDC with 6 decimals). No API keys, rate limits, or upfront commitments are required — callers simply attach an x402 payment header to each request.\n\nThe broader platform advertises four categories of endpoints: 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 listed endpoints share the same $0.02/request pricing.\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 example payloads available. The x402 challenge confirms the endpoint is live and accepts POST requests, but the actual functionality behind `/api/v1/cards/20` is unclear — the name \"Premium API Access\" and the path segment \"cards/20\" do not map obviously to any of the advertised API categories.","tags":[],"capabilities":["x402-payment","usdc-settlement","base-network","pay-per-request","no-api-key","post-method"],"categories":["api-gateway","misc"],"synonyms":["low payment fee","x402 api","micropayment api","pay-per-call api","USDC api","base network api","402 payment api"],"warnings":["No OpenAPI spec or request/response schema available","All documentation pages (/docs, /api, /pricing, /README) render only 'Connect wallet' with no content","The purpose and expected input/output of /api/v1/cards/20 ('Premium API Access') is unclear and does not match any of the advertised API categories","No examples or error documentation found"],"endpointUrl":"https://lowpaymentfee.com/api/v1/cards/20","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/cards/20","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.300","qualityRationale":"The x402 challenge is live and pricing is clear ($0.02 USDC on Base), but there is zero documentation on request/response schemas, no OpenAPI spec, and the specific purpose of the /cards/20 endpoint is unexplained. The docs pages are empty beyond a wallet-connect prompt. This is effectively a stub 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'/api/v1/cards/20':60,205 '/docs':156 '/pricing':158 '/readme':160 '/request':16,32,149 '0.02':15,31,69,148 '000':73 '20':72 '402 payment api' '6':79 'USDC api' 'accept':197 'access':66,212 'actual':202 'advertis':104,226 'ai':9,25,116 'analysi':120 'analyt':8,24,110 'api':4,20,42,65,82,211,227 'attach':93 'avail':187 'base':7,23,55,74 'base network api' 'base-network' 'behind':204 'broader':102 'call':41 'caller':91 'cards/20':217 'categori':106,228 'challeng':190 'classif':123 'collect':36 'commit':88 'confirm':191 'connect':166 'convers':140 'cost':68 'data':109,113 'decim':80 'detail':173 'document':151,182 'embed':124 'endpoint':13,29,43,59,108,144,193 'estim':134 'exampl':185 'exchang':129 'export':114 'extrem':153 'feed':128 'financ':10,26,125 'four':105 'function':203 'gas':133 'gate':3,19,44 'generat':141 'geocod':138 'header':97 'infrastructur':136 'insight':115 'key':83 'learn':118 'limit':85 'list':62,143 'live':195 'low payment fee' 'lowpaymentfee.com':33 'machin':117 'map':220 'metric':111 'micropayment api' 'name':209 'network':56 'no-api-key' 'obvious':221 'offer':34 'openapi':177 'page':161 'path':215 'pay':39 'pay-per-cal':38 'pay-per-call api' 'pay-per-request' 'payload':186 'payment':50,96 'per':40,70 'platform':103 'post':198 'post-method' 'premium':64,210 'price':127,150 'prompt':168 'protocol':48 'quot':132 'rate':84,130 'render':163 'report':112 'request':71,100,199 'request/response':180 'requir':90 'schema':181 'segment':216 'sentiment':119 'settl':49 'share':145 'simpli':92 'spars':154 'spec':178 'specif':58 'suit':5,21 'summar':122 'technic':172 'text':121 'token':131 'unclear':207 'unit':75 'upfront':87 'usdc':52,77 'usdc-settlement' 'util':12,28,137 'valid':139 'wallet':167 'web3':126 'x402':2,18,47,95,189 'x402 api' 'x402-gated':1,17 'x402-payment'","prices":[{"id":"4512b8c0-45f3-453c-af96-81368b5c82b1","listingId":"9153ce6f-d1d5-437d-81e3-2cef95cc866b","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/cards/20","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:43:25.592Z"}],"sources":[{"listingId":"9153ce6f-d1d5-437d-81e3-2cef95cc866b","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/cards/20","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:43:25.592Z","lastSeenAt":"2026-04-22T10:31:28.270Z"}],"details":{"listingId":"9153ce6f-d1d5-437d-81e3-2cef95cc866b","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/cards/20 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <x402-payment-token>\"","exampleRequest":null,"exampleResponse":null,"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"The endpoint returns a 402 challenge with maxAmountRequired of 20000 base units of USDC on Base network","source_url":"https://lowpaymentfee.com/api/v1/cards/20"},{"claim":"All listed endpoints are priced at $0.02 per request with no API keys, rate limits, or commitments","source_url":"https://lowpaymentfee.com"},{"claim":"The platform advertises Data & Analytics, AI & ML, Finance & Web3, and Infrastructure endpoint categories","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base network","source_url":"https://lowpaymentfee.com/api/v1/cards/20"}],"useCases":["Programmatic access to pay-per-call endpoints without managing API keys or subscriptions","Agent-driven workflows that need on-demand API calls settled in USDC on Base","Exploring x402 protocol integration with a low-cost test endpoint"],"bestFor":["Developers experimenting with x402 payment protocol","Agents that need keyless, pay-as-you-go API access on Base","Low-volume callers who prefer per-request billing over subscriptions"],"notFor":["Users who need detailed API documentation or OpenAPI specs before integrating","High-volume production workloads requiring SLAs or guaranteed uptime","Anyone needing clarity on what data or functionality the /cards/20 endpoint actually returns"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:27.349Z"},"updatedAt":"2026-04-22T10:31:28.270Z"}}