{"id":"5f6cfbfc-f3f1-4867-9a1d-ae6d9f2a2320","shortId":"D5N6J6","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/15` 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/15` 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 advertised — access is gated purely by on-chain micropayment. 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, pricing, API, and README pages all render only a \"Connect wallet\" prompt with no substantive content. Because the specific behavior of `/api/v1/carts/15` is undocumented and the \"Premium API Access\" label is generic, the actual data returned by this endpoint remains unclear.","tags":[],"capabilities":["x402-payment","usdc-payment","base-network","pay-per-request","json-response","no-api-key","post-method"],"categories":["api-marketplace","crypto"],"synonyms":["x402 API","pay-per-call API","USDC micropayment API","Base network API","lowpaymentfee","premium API access","crypto-gated endpoint"],"warnings":["The specific functionality of /api/v1/carts/15 ('Premium API Access') is not documented anywhere — the label is generic and uninformative.","All documentation pages (docs, pricing, API, README) render only a 'Connect wallet' prompt with no substantive content.","No request body schema or response schema is available; callers cannot know what to send or what to expect back.","The endpoint path '/carts/15' suggests a resource tied to a specific cart ID, which may be ephemeral or user-specific."],"endpointUrl":"https://lowpaymentfee.com/api/v1/carts/15","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/15","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 the actual functionality behind \"Premium API Access\" at /carts/15 is completely undocumented. Docs pages render only a wallet-connect prompt with no content. No request/response schema, no examples, and no description of what data is 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'/carts/15':61 '0.02':83,114 '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913':142 '16':179 '20000':104 '300':172 '6':118 'Base network API' 'USDC micropayment API' 'accept':137,162 'access':67,151,218 'across':89,181 'actual':223 'advertis':80,150 'ai/ml':53 'analyt':52 'api':5,18,49,66,144,191,217 'application/json':167 'asset':138 'base':8,21,107,110,133 'base-network' 'behavior':209 'beyond':75 'broader':175 'categori':183 'chain':158 'challeng':99 'collect':40 'connect':199 'content':205 'contract':141 'crypto-gated endpoint' 'data':51,224 'decim':119 'doc':189 'document':74,187 'endpoint':6,19,28,62,92,96,161,180,228 'equal':113 'exact':70,129 'finance/web3':55 'flat':82 'four':182 'function':71 'gate':3,16,153 'generic':221 'given':115 'handl':122 'infer':54 'infrastructur':57 'json-response' 'key':145 'l2':134 'label':64,77,219 'limit':148 'list':178 'lowpaymentfee' 'lowpaymentfee.com':35,176 'maxamountrequir':102 'micropay':159 'minim':186 'model':88 'network':111,135 'no-api-key' 'offer':38 'on-chain':156 'page':194 'part':32 'particular':95 'pay':46 'pay-per-call API' 'pay-per-request':45 'payabl':9,22 'payment':120,169 'per':12,25,47,85 'per-request':84 'platform':36,79,177 'post':163 'post-method' 'premium':4,17,65,216 'premium API access' 'price':87,190 'prompt':201 'protocol':44,126 'provid':185 'pure':154 'rate':147 'readm':193 'remain':229 'render':196 'request':13,26,48,86,164 'return':166,225 'scheme':130 'second':173 'span':50 'specif':60,208 'specifi':100 'substant':204 'though':93 'timeout':170 'unclear':230 'undocu':213 'unit':108 'usdc':11,24,106,116,140 'usdc-payment' 'use':127 'util':58 'via':123 'wallet':200 'x402':2,15,43,98,125 'x402 API' 'x402-gated':1,14 'x402-payment' 'x402-protocol':42","prices":[{"id":"14bc1d9b-e3fd-4f4b-81b8-566e5c508994","listingId":"5f6cfbfc-f3f1-4867-9a1d-ae6d9f2a2320","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/15","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:32:11.707Z"}],"sources":[{"listingId":"5f6cfbfc-f3f1-4867-9a1d-ae6d9f2a2320","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/carts/15","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:32:11.707Z","lastSeenAt":"2026-04-23T22:01:42.318Z"}],"details":{"listingId":"5f6cfbfc-f3f1-4867-9a1d-ae6d9f2a2320","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/carts/15 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <x402-payment-header>\"","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 x402Version 1, exact scheme, on Base network, accepting USDC at maxAmountRequired 20000","source_url":"https://lowpaymentfee.com/api/v1/carts/15"},{"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 USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/carts/15"},{"claim":"Docs, pricing, API, and README pages render only a 'Connect wallet' prompt","source_url":"https://lowpaymentfee.com/docs"}],"useCases":["Accessing a premium API resource via on-chain USDC micropayment without needing an API key","Agent-driven programmatic purchasing of API responses using x402 protocol","Demonstrating x402 pay-per-request integration on Base network"],"bestFor":["Developers experimenting with x402 protocol micropayments","Agents that can settle USDC payments on Base L2","Use cases requiring keyless, pay-as-you-go API access"],"notFor":["Users who need detailed documentation or guaranteed SLAs before integrating","Applications requiring free or fiat-only payment methods","Production workloads needing well-documented response schemas"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:15:00.394Z"},"updatedAt":"2026-04-23T22:01:42.318Z"}}