{"id":"5d76ed9f-170a-47e9-8496-f43a1c8c122c","shortId":"W4GCPY","kind":"x402","title":"x402-gated card-transaction endpoint on Base, paying $0.02 per request in USDC.","tagline":"x402-gated card-transaction endpoint on Base, paying $0.02 per request in USDC.","description":"This endpoint at lowpaymentfee.com exposes a card-transactions resource at `/api/v1/cards/16/transactions` behind an x402 payment challenge. It is part of a broader platform (lowpaymentfee.com) that offers dozens of pay-per-call APIs spanning data analytics, AI/ML inference, finance/Web3 data, and infrastructure utilities — all gated via the x402 protocol on the Base network.\n\nThe specific endpoint accepts POST requests and requires an X-PAYMENT header carrying an x402 payment proof. The challenge advertises a maximum amount of 20,000 base units of USDC (contract 0x8335…2913 on Base), which at 6 decimals equals $0.02 per request. Payment is settled on-chain to address 0x1A2B…85F3. The platform advertises no API keys, no rate limits, and instant access — you pay per call and that's it.\n\nDocumentation is extremely thin: the docs, API, pricing, and README pages all render only a \"Connect wallet\" prompt with no further content. There is no OpenAPI spec, no request/response schema, and no usage examples available from the crawl. The endpoint's purpose — retrieving or creating transactions for \"card 16\" — is not explained anywhere in the crawled material. Without documentation it is unclear what request body fields are expected or what the response looks like.","tags":[],"capabilities":["x402-payment","usdc-settlement","base-network","card-transactions","pay-per-request","no-api-key"],"categories":["finance","payments"],"synonyms":["card transactions API","x402 payment API","USDC micropayment endpoint","lowpaymentfee","pay-per-call API","Base network API","card 16 transactions"],"warnings":["No documentation available — docs, API, pricing, and README pages all show only 'Connect wallet' with no content.","No OpenAPI or request/response schema provided; request body format is unknown.","The specific purpose of /api/v1/cards/16/transactions is not documented anywhere in crawled material.","This endpoint path references a hardcoded resource ID (card 16) with no explanation of what it represents."],"endpointUrl":"https://lowpaymentfee.com/api/v1/cards/16/transactions","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/16/transactions","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.250","qualityRationale":"The endpoint is live (402 challenge confirmed) and pricing is clear ($0.02 USDC on Base), but there is zero documentation on request/response schemas, no OpenAPI spec, and the docs pages are empty. The purpose of 'cards/16/transactions' is unexplained. This is effectively a stub 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'0.02':11,26,126 '000':111 '0x1a2b':137 '0x8335':117 '16':207 '20':110 '2913':118 '6':123 '85f3':138 'Base network API' 'USDC micropayment endpoint' 'accept':88 'access':150 'address':136 'advertis':105,141 'ai/ml':68 'amount':108 'analyt':67 'anywher':211 'api':64,143,165 'avail':193 'base':9,24,83,112,120 'base-network' 'behind':43 'bodi':223 'broader':53 'call':63,154 'card':5,20,38,206 'card 16 transactions' 'card transactions API' 'card-transact':4,19,37 'card-transactions' 'carri':98 'chain':134 'challeng':47,104 'connect':174 'content':180 'contract':116 'crawl':196,214 'creat':203 'data':66,71 'decim':124 'doc':164 'document':159,217 'dozen':58 'endpoint':7,22,32,87,198 'equal':125 'exampl':192 'expect':226 'explain':210 'expos':35 'extrem':161 'field':224 'finance/web3':70 'gate':3,18,76 'header':97 'infer':69 'infrastructur':73 'instant':149 'key':144 'like':232 'limit':147 'look':231 'lowpaymentfee' 'lowpaymentfee.com':34,55 'materi':215 'maximum':107 'network':84 'no-api-key' 'offer':57 'on-chain':132 'openapi':184 'page':169 'part':50 'pay':10,25,61,152 'pay-per-cal':60 'pay-per-call API' 'pay-per-request' 'payment':46,96,101,129 'per':12,27,62,127,153 'platform':54,140 'post':89 'price':166 'prompt':176 'proof':102 'protocol':80 'purpos':200 'rate':146 'readm':168 'render':171 'request':13,28,90,128,222 'request/response':187 'requir':92 'resourc':40 'respons':230 'retriev':201 'schema':188 'settl':131 'span':65 'spec':185 'specif':86 'thin':162 'transact':6,21,39,204 'unclear':220 'unit':113 'usag':191 'usdc':15,30,115 'usdc-settlement' 'util':74 'via':77 'wallet':175 'without':216 'x':95 'x-payment':94 'x402':2,17,45,79,100 'x402 payment API' 'x402-gated':1,16 'x402-payment'","prices":[{"id":"1c45899a-6ede-4f45-8823-03e4327e4bdd","listingId":"5d76ed9f-170a-47e9-8496-f43a1c8c122c","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/16/transactions","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:43:14.690Z"}],"sources":[{"listingId":"5d76ed9f-170a-47e9-8496-f43a1c8c122c","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/cards/16/transactions","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:43:14.690Z","lastSeenAt":"2026-04-24T22:32:14.459Z"}],"details":{"listingId":"5d76ed9f-170a-47e9-8496-f43a1c8c122c","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/cards/16/transactions \\\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 endpoint returns a 402 challenge with maxAmountRequired of 20000 base units of USDC on Base network.","source_url":"https://lowpaymentfee.com/api/v1/cards/16/transactions"},{"claim":"The platform advertises $0.02 per request, no API keys, no rate limits, and instant access on Base network.","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913.","source_url":"https://lowpaymentfee.com/api/v1/cards/16/transactions"}],"useCases":["Querying or creating card transaction records via a pay-per-call model","Integrating card transaction data into agent workflows without API key management","Demonstrating x402 protocol payment flows on Base"],"bestFor":["Developers experimenting with x402 payment-gated APIs","Agents that need keyless, pay-per-request access to card transaction data","Projects already operating on the Base L2 with USDC"],"notFor":["Production use cases requiring documented request/response schemas","Users who need free or subscription-based access without per-call crypto payments","Anyone needing detailed card transaction analytics with well-documented fields"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:27.855Z"},"updatedAt":"2026-04-24T22:32:14.459Z"}}