{"id":"1264bb95-cb92-4d75-b437-cc84c92f6455","shortId":"hFQmqB","kind":"x402","title":"Pay-per-call portfolio transactions endpoint on Base via x402 (USDC, $0.02/request).","tagline":"Pay-per-call portfolio transactions endpoint on Base via x402 (USDC, $0.02/request).","description":"This x402-enabled endpoint at lowpaymentfee.com provides access to portfolio transaction data via a POST request to `/api/v1/portfolios/21/transactions`. It is part of a broader platform offering data & analytics, AI/ML inference, finance/Web3, and infrastructure utility APIs, all priced at $0.02 per request with no API keys, no rate limits, and no commitments required.\n\nPayment is settled on the Base network using USDC (contract `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`). The x402 challenge specifies a `maxAmountRequired` of 20,000 base units, which at 6 decimals equals $0.02 USD per call. The endpoint uses the \"exact\" payment scheme with a 300-second timeout. No OpenAPI schema or detailed documentation was found for this specific endpoint beyond the x402 challenge metadata.\n\nThe specific endpoint listed here (`/api/v1/portfolios/21/transactions`) appears to be a portfolio-specific transactions resource, likely returning or accepting transaction records for portfolio ID 21. However, the request and response schemas are not documented, so the exact input format and output structure are unknown. The broader platform advertises categories including finance, crypto, AI, and utility endpoints, all following the same x402 payment pattern.","tags":[],"capabilities":["x402-payment","usdc-settlement","base-network","portfolio-transactions","pay-per-call","no-api-key","post-endpoint"],"categories":["finance","data"],"synonyms":["portfolio transactions API","x402 finance endpoint","USDC micropayment API","Base network API","pay-per-request transactions","lowpaymentfee API","crypto portfolio data"],"warnings":["No OpenAPI or request/response schema available for this endpoint","Documentation pages (/docs, /api, /pricing, /README) returned no useful content","The endpoint path references a hardcoded portfolio ID (21), which may not be generalizable","Exact input format and response structure are unknown"],"endpointUrl":"https://lowpaymentfee.com/api/v1/portfolios/21/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/portfolios/21/transactions","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.350","qualityRationale":"The endpoint is live and returns a valid x402 challenge with clear pricing, but there is no OpenAPI schema, no request/response documentation, and the crawled docs/pricing/API pages are all empty (just 'Connect wallet'). The purpose of this specific endpoint (portfolios/21/transactions) is unclear beyond the generic 'Premium API Access' 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'/request':14,28 '0.02':13,27,68,109 '000':101 '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913':92 '20':100 '21':166 '300':122 '6':106 'Base network API' 'USDC micropayment API' 'accept':160 'access':37 'advertis':189 'ai':194 'ai/ml':58 'analyt':57 'api':64,73 'appear':148 'base':9,23,87,102 'base-network' 'beyond':137 'broader':53,187 'call':4,18,112 'categori':190 'challeng':95,140 'commit':80 'contract':91 'crypto':193 'crypto portfolio data' 'data':41,56 'decim':107 'detail':129 'document':130,175 'enabl':32 'endpoint':7,21,33,114,136,144,197 'equal':108 'exact':117,178 'financ':192 'finance/web3':60 'follow':199 'format':180 'found':132 'howev':167 'id':165 'includ':191 'infer':59 'infrastructur':62 'input':179 'key':74 'like':157 'limit':77 'list':145 'lowpaymentfee API' 'lowpaymentfee.com':35 'maxamountrequir':98 'metadata':141 'network':88 'no-api-key' 'offer':55 'openapi':126 'output':182 'part':50 'pattern':204 'pay':2,16 'pay-per-cal':1,15 'pay-per-call' 'pay-per-request transactions' 'payment':82,118,203 'per':3,17,69,111 'platform':54,188 'portfolio':5,19,39,153,164 'portfolio transactions API' 'portfolio-specif':152 'portfolio-transactions' 'post':44 'post-endpoint' 'price':66 'provid':36 'rate':76 'record':162 'request':45,70,169 'requir':81 'resourc':156 'respons':171 'return':158 'schema':127,172 'scheme':119 'second':123 'settl':84 'specif':135,143,154 'specifi':96 'structur':183 'timeout':124 'transact':6,20,40,155,161 'unit':103 'unknown':185 'usd':110 'usdc':12,26,90 'usdc-settlement' 'use':89,115 'util':63,196 'via':10,24,42 'x402':11,25,31,94,139,202 'x402 finance endpoint' 'x402-enabled':30 'x402-payment'","prices":[{"id":"f6363915-01c0-4052-bb2d-4e23dee2b41f","listingId":"1264bb95-cb92-4d75-b437-cc84c92f6455","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/portfolios/21/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":"2026-04-18T18:52:34.512Z"}],"sources":[{"listingId":"1264bb95-cb92-4d75-b437-cc84c92f6455","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/portfolios/21/transactions","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:52:34.512Z","lastSeenAt":"2026-04-28T03:05:37.535Z"}],"details":{"listingId":"1264bb95-cb92-4d75-b437-cc84c92f6455","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/portfolios/21/transactions \\\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 x402 challenge specifies maxAmountRequired of 20000 base units in USDC on Base network","source_url":"https://lowpaymentfee.com/api/v1/portfolios/21/transactions"},{"claim":"All APIs on the platform are priced at $0.02 per request with no API keys, no rate limits, and instant access","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/portfolios/21/transactions"}],"useCases":["Retrieving or submitting transaction records for a specific portfolio","Integrating portfolio transaction data into automated trading or analytics pipelines","Agent-driven portfolio management workflows that pay per API call with USDC"],"bestFor":["Developers wanting keyless, pay-per-call access to portfolio transaction data","AI agents that can settle x402 payments on Base with USDC","Projects needing low-cost API access without subscription commitments"],"notFor":["Users who need detailed API documentation or OpenAPI specs before integrating","High-volume use cases where $0.02/request adds up significantly","Users without USDC on the Base network"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:00.864Z"},"updatedAt":"2026-04-28T03:05:37.535Z"}}