{"id":"9712698b-0385-4765-9360-5a51bf97fa39","shortId":"DTzWkC","kind":"x402","title":"x402-gated premium API endpoint on Base, pay-per-call with USDC.","tagline":"x402-gated premium API endpoint on Base, pay-per-call with USDC.","description":"This endpoint at `/api/v1/cards/31` is part of the lowpaymentfee.com platform, a collection of x402-protocol pay-per-request APIs spanning data analytics, AI/ML inference, finance/Web3, and infrastructure utilities. The specific `/api/v1/cards/31` resource is labeled \"Premium API Access\" but its exact functionality is not documented beyond that title — it is one of many endpoints on the platform, all gated behind x402 micropayments settled in USDC on the Base network.\n\nThe x402 challenge confirms the endpoint is live and accepts POST requests. The maximum amount required is 20,000 base units of USDC (the asset at 0x8335… is Base USDC with 6 decimals), which equals $0.02 per request. The platform advertises uniform $0.02/request pricing across all endpoints, with no API keys, no rate limits, and no minimum commitments. Payment is made via the x402 `exact` scheme to the specified payTo address.\n\nBecause the crawled documentation pages (docs, api, pricing, README) all returned only a \"Connect wallet\" prompt with no further content, the actual input/output schema and behavior of this specific endpoint remain unknown. The platform lists categories like Data & Analytics, AI & ML, Finance & Web3, and Infrastructure, but `/api/v1/cards/31` does not appear in any of those listed routes, making its purpose unclear. Treat this as a stub listing until more documentation becomes available.","tags":[],"capabilities":["x402-payment","usdc-base","pay-per-request","post-endpoint","micropayment-gated"],"categories":["api-marketplace","payments"],"synonyms":["lowpaymentfee","x402 api","micropayment api","base usdc api","pay per call api","cards endpoint"],"warnings":["The endpoint /api/v1/cards/31 is not listed among the platform's documented API routes — its purpose is unknown.","All documentation pages (docs, api, pricing, README) returned only 'Connect wallet' with no usable content.","No input or output schema is available; the actual response payload after successful payment is unknown.","The 'Premium API Access' label is generic and does not describe functionality."],"endpointUrl":"https://lowpaymentfee.com/api/v1/cards/31","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/31","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 via a valid 402 challenge, and pricing is clear ($0.02/request in USDC on Base). However, the specific functionality of /api/v1/cards/31 is entirely undocumented — it doesn't appear in the site's listed endpoints, there is no input/output schema, and all documentation pages returned only 'Connect wallet' with no content. This is effectively a 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'/request':142 '0.02':134,141 '000':117 '0x8335':125 '20':116 '6':130 'accept':108 'access':67 'across':144 'actual':192 'address':170 'advertis':139 'ai':210 'ai/ml':53 'amount':113 'analyt':52,209 'api':5,19,49,66,149,177 'appear':220 'asset':123 'avail':241 'base':8,22,97,118,127 'base usdc api' 'becom':240 'behavior':196 'behind':89 'beyond':75 'call':12,26 'cards endpoint' 'categori':206 'challeng':101 'collect':40 'commit':157 'confirm':102 'connect':184 'content':190 'crawl':173 'data':51,208 'decim':131 'doc':176 'document':74,174,239 'endpoint':6,20,30,83,104,146,200 'equal':133 'exact':70,164 'financ':212 'finance/web3':55 'function':71 'gate':3,17,88 'infer':54 'infrastructur':57,215 'input/output':193 'key':150 'label':64 'like':207 'limit':153 'list':205,225,236 'live':106 'lowpaymentfee' 'lowpaymentfee.com':37 'made':160 'make':227 'mani':82 'maximum':112 'micropay':91 'micropayment api' 'micropayment-gated' 'minimum':156 'ml':211 'network':98 'one':80 'page':175 'part':34 'pay':10,24,46 'pay per call api' 'pay-per-cal':9,23 'pay-per-request':45 'payment':158 'payto':169 'per':11,25,47,135 'platform':38,86,138,204 'post':109 'post-endpoint' 'premium':4,18,65 'price':143,178 'prompt':186 'protocol':44 'purpos':229 'rate':152 'readm':179 'remain':201 'request':48,110,136 'requir':114 'resourc':62 'return':181 'rout':226 'schema':194 'scheme':165 'settl':92 'span':50 'specif':60,199 'specifi':168 'stub':235 'titl':77 'treat':231 'unclear':230 'uniform':140 'unit':119 'unknown':202 'usdc':14,28,94,121,128 'usdc-base' 'util':58 'via':161 'wallet':185 'web3':213 'x402':2,16,43,90,100,163 'x402 api' 'x402-gated':1,15 'x402-payment' 'x402-protocol':42","prices":[{"id":"b6543131-bd9f-45d8-bfaf-b57e337daf98","listingId":"9712698b-0385-4765-9360-5a51bf97fa39","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/31","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:43:29.219Z"}],"sources":[{"listingId":"9712698b-0385-4765-9360-5a51bf97fa39","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/cards/31","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:43:29.219Z","lastSeenAt":"2026-04-23T04:31:07.451Z"}],"details":{"listingId":"9712698b-0385-4765-9360-5a51bf97fa39","quickStartSnippet":"# 1. Send a POST to discover the x402 payment challenge\ncurl -X POST https://lowpaymentfee.com/api/v1/cards/31\n# Returns 402 with X-Payment challenge in JSON body\n# 2. Construct and attach the X-PAYMENT header per x402 spec, then re-send the POST","exampleRequest":null,"exampleResponse":{"error":"X-PAYMENT header is required","accepts":[{"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","extra":{"name":"USD Coin","version":"2"},"payTo":"0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3","scheme":"exact","network":"base","mimeType":"application/json","resource":"https://lowpaymentfee.com/api/v1/cards/31","description":"Premium API Access","maxAmountRequired":"20000","maxTimeoutSeconds":300}],"x402Version":1},"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"The platform advertises $0.02/request pricing with no API keys, no rate limits, and instant access on Base network.","source_url":"https://lowpaymentfee.com"},{"claim":"The x402 challenge returns maxAmountRequired of 20000 base units of USDC (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base, equaling $0.02.","source_url":"https://lowpaymentfee.com/api/v1/cards/31"},{"claim":"Documentation pages at /docs, /api, /pricing, and /README returned only 'Connect wallet' with no further content.","source_url":"https://lowpaymentfee.com/docs"}],"useCases":["Accessing a premium pay-per-call API resource without API keys or subscriptions","Making micropayment-gated requests settled in USDC on Base","Programmatic agent-driven API consumption via x402 protocol"],"bestFor":["Developers wanting zero-signup, pay-as-you-go API access","AI agents that can settle x402 micropayments on Base","Users who prefer crypto-native per-request billing over subscriptions"],"notFor":["Users who need detailed documentation or guaranteed SLAs before integrating","Anyone requiring non-crypto payment methods","Use cases requiring known, well-documented input/output schemas"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:27.181Z"},"updatedAt":"2026-04-23T04:31:07.451Z"}}