{"id":"0c457c03-cb74-4f4c-97b9-993f0e98526f","shortId":"X66arh","kind":"x402","title":"x402-gated premium API endpoint on Base, payable in USDC per request.","tagline":"x402-gated premium API endpoint on Base, payable in USDC per request.","description":"This endpoint at `/api/v1/carts/14` is part of the lowpaymentfee.com platform, which offers a collection of x402-protocol pay-per-request APIs spanning data & analytics, AI/ML inference, finance & Web3, and infrastructure utilities. The specific `/carts/14` endpoint is labeled \"Premium API Access\" but its exact functionality is not documented beyond that label. The platform advertises a flat $0.02 per request pricing model across its other endpoints, though this particular endpoint's x402 challenge specifies a `maxAmountRequired` of 20000 (in USDC base units on Base network, which equals $0.02 given USDC's 6 decimals).\n\nPayment is handled via the x402 protocol using the \"exact\" scheme on the Base L2 network. The accepted asset is USDC (contract `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`). No API keys or rate limits are required — callers simply attach an `X-PAYMENT` header with a valid payment proof. The endpoint accepts POST requests and returns `application/json`. The payment timeout is 300 seconds.\n\nThe broader lowpaymentfee.com platform lists 16 endpoints across four categories but provides minimal documentation — the docs, API, pricing, and README pages all render only a \"Connect wallet\" prompt with no substantive content. Because the specific purpose of `/api/v1/carts/14` is unclear (it does not appear in the site's listed API catalog), its actual functionality cannot be confirmed from available sources.","tags":[],"capabilities":["x402-payment","usdc-payment","base-network","pay-per-request","json-response","post-method"],"categories":["api","payments"],"synonyms":["x402 API","pay-per-call API","USDC API","Base network API","lowpaymentfee","micropayment API","402 payment required"],"warnings":["The endpoint /api/v1/carts/14 is not listed among the platform's advertised APIs — its specific functionality is unknown.","All documentation pages (docs, API, pricing, README) return only a 'Connect wallet' prompt with no actual content.","No request body schema or response schema is documented; callers cannot know what to send or expect back.","The 'Premium API Access' label is generic and does not describe what the endpoint does."],"endpointUrl":"https://lowpaymentfee.com/api/v1/carts/14","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/carts/14","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 confirmed) and pricing is clear ($0.02 USDC on Base), but the actual functionality of /api/v1/carts/14 is undocumented — it doesn't appear in the site's own API catalog. Documentation pages are empty (just 'Connect wallet'). No request/response schema, no examples, and no OpenAPI spec are 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'/carts/14':62 '0.02':84,114 '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913':142 '16':183 '20000':104 '300':176 '402 payment required' '6':118 'Base network API' 'USDC API' 'accept':137,166 'access':68 'across':89,185 'actual':230 'advertis':81 'ai/ml':53 'analyt':52 'api':5,18,49,67,144,194,227 'appear':221 'application/json':171 'asset':138 'attach':153 'avail':236 'base':8,21,107,110,133 'base-network' 'beyond':76 'broader':179 'caller':151 'cannot':232 'catalog':228 'categori':187 'challeng':99 'collect':40 'confirm':234 'connect':203 'content':209 'contract':141 'data':51 'decim':119 'doc':193 'document':75,191 'endpoint':6,19,28,63,92,96,165,184 'equal':113 'exact':71,129 'financ':55 'flat':83 'four':186 'function':72,231 'gate':3,16 'given':115 'handl':122 'header':158 'infer':54 'infrastructur':58 'json-response' 'key':145 'l2':134 'label':65,78 'limit':148 'list':182,226 'lowpaymentfee' 'lowpaymentfee.com':35,180 'maxamountrequir':102 'micropayment API' 'minim':190 'model':88 'network':111,135 'offer':38 'page':198 'part':32 'particular':95 'pay':46 'pay-per-call API' 'pay-per-request':45 'payabl':9,22 'payment':120,157,162,173 'per':12,25,47,85 'platform':36,80,181 'post':167 'post-method' 'premium':4,17,66 'price':87,195 'prompt':205 'proof':163 'protocol':44,126 'provid':189 'purpos':213 'rate':147 'readm':197 'render':200 'request':13,26,48,86,168 'requir':150 'return':170 'scheme':130 'second':177 'simpli':152 'site':224 'sourc':237 'span':50 'specif':61,212 'specifi':100 'substant':208 'though':93 'timeout':174 'unclear':217 'unit':108 'usdc':11,24,106,116,140 'usdc-payment' 'use':127 'util':59 'valid':161 'via':123 'wallet':204 'web3':56 'x':156 'x-payment':155 'x402':2,15,43,98,125 'x402 API' 'x402-gated':1,14 'x402-payment' 'x402-protocol':42","prices":[{"id":"f2c0dbb9-7b90-4742-aed2-f89be8a09bf6","listingId":"0c457c03-cb74-4f4c-97b9-993f0e98526f","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/carts/14","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:32:10.495Z"}],"sources":[{"listingId":"0c457c03-cb74-4f4c-97b9-993f0e98526f","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/carts/14","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:32:10.495Z","lastSeenAt":"2026-04-23T02:00:18.854Z"}],"details":{"listingId":"0c457c03-cb74-4f4c-97b9-993f0e98526f","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/carts/14 \\\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":"The x402 challenge returns maxAmountRequired of 20000 USDC base units on Base network with the exact scheme","source_url":"https://lowpaymentfee.com/api/v1/carts/14"},{"claim":"The platform advertises $0.02 per request pricing with no API keys, no rate limits, and instant access","source_url":"https://lowpaymentfee.com"},{"claim":"The USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base","source_url":"https://lowpaymentfee.com/api/v1/carts/14"},{"claim":"Documentation, API, pricing, and README pages render only a 'Connect wallet' prompt","source_url":"https://lowpaymentfee.com/docs"}],"useCases":["Programmatic access to a premium API resource with per-request USDC micropayments","Agent-driven workflows that need keyless, on-demand API access on Base","Demonstrating x402 protocol payment flows in development or testing"],"bestFor":["Developers experimenting with x402 pay-per-request protocols","Agents that can sign USDC payments on Base L2","Use cases requiring no-signup, no-API-key access"],"notFor":["Users who need detailed API documentation before integrating","High-volume use cases where per-request payment overhead is impractical","Anyone without a Base-network USDC wallet"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:15:00.402Z"},"updatedAt":"2026-04-23T02:00:18.854Z"}}