{"id":"c21e1605-eea5-4bf9-aea1-7745c5ebd3e9","shortId":"VQbDsa","kind":"x402","title":"x402-gated portfolio transactions endpoint on Base, pay-per-call with USDC.","tagline":"x402-gated portfolio transactions endpoint on Base, pay-per-call with USDC.","description":"This endpoint at lowpaymentfee.com exposes a POST-based portfolio transactions API at `/api/v1/portfolios/15/transactions`, gated by the x402 payment protocol. Each call costs up to $0.02 USDC (maxAmountRequired of 20,000 base units with 6 decimals) settled on the Base network. No API keys or rate limits are required — callers simply attach an X-PAYMENT header with a valid x402 payment proof.\n\nThe endpoint is part of a broader platform (lowpaymentfee.com) that offers dozens of pay-per-request APIs spanning data analytics, AI/ML inference, finance/Web3 data, and utility services, all priced at $0.02 per request. However, the specific `/portfolios/15/transactions` path is not listed on the site's public catalog, and no documentation describes its request or response schema. The \"Premium API Access\" label is the only description provided by the x402 challenge.\n\nBecause there is no OpenAPI spec, no request/response schema documentation, and the crawled docs/pricing/API pages all returned only a \"Connect wallet\" stub, the actual functionality of this particular endpoint is unclear. It likely involves creating or retrieving transactions for a specific portfolio (ID 15), but the exact input fields and output format are unknown. Callers should treat this as an exploratory endpoint until more documentation surfaces.","tags":[],"capabilities":["x402-payment","usdc-settlement","base-network","portfolio-transactions","pay-per-request","no-api-key"],"categories":["finance","payments"],"synonyms":["portfolio transactions API","x402 paid endpoint","USDC micropayment API","Base network API","pay-per-call transactions","lowpaymentfee"],"warnings":["No request or response schema documented — callers must guess at the POST body format","This specific endpoint (/api/v1/portfolios/15/transactions) is not listed in the site's public API catalog","All documentation pages (docs, api, pricing, README) returned only a 'Connect wallet' stub with no useful content","The hardcoded portfolio ID '15' in the path suggests this may be a demo or single-tenant endpoint"],"endpointUrl":"https://lowpaymentfee.com/api/v1/portfolios/15/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/15/transactions","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 there is zero documentation on request/response schema, no OpenAPI spec, and the crawled pages are mostly empty stubs. The specific portfolio transactions path is not even listed in the site's own catalog, making this effectively a stub 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'/portfolios/15/transactions':129 '0.02':54,123 '000':59 '15':206 '20':58 '6':63 'Base network API' 'USDC micropayment API' 'access':152 'actual':186 'ai/ml':113 'analyt':112 'api':40,71,109,151 'attach':80 'base':8,22,37,60,68 'base-network' 'broader':98 'call':12,26,50 'caller':78,217 'catalog':139 'challeng':162 'connect':182 'cost':51 'crawl':175 'creat':197 'data':111,116 'decim':64 'describ':143 'descript':157 'docs/pricing/api':176 'document':142,172,227 'dozen':103 'endpoint':6,20,30,93,191,224 'exact':209 'exploratori':223 'expos':33 'field':211 'finance/web3':115 'format':214 'function':187 'gate':3,17,43 'header':85 'howev':126 'id':205 'infer':114 'input':210 'involv':196 'key':72 'label':153 'like':195 'limit':75 'list':133 'lowpaymentfee' 'lowpaymentfee.com':32,100 'maxamountrequir':56 'network':69 'no-api-key' 'offer':102 'openapi':167 'output':213 'page':177 'part':95 'particular':190 'path':130 'pay':10,24,106 'pay-per-cal':9,23 'pay-per-call transactions' 'pay-per-request':105 'payment':47,84,90 'per':11,25,107,124 'platform':99 'portfolio':4,18,38,204 'portfolio transactions API' 'portfolio-transactions' 'post':36 'post-bas':35 'premium':150 'price':121 'proof':91 'protocol':48 'provid':158 'public':138 'rate':74 'request':108,125,145 'request/response':170 'requir':77 'respons':147 'retriev':199 'return':179 'schema':148,171 'servic':119 'settl':65 'simpli':79 'site':136 'span':110 'spec':168 'specif':128,203 'stub':184 'surfac':228 'transact':5,19,39,200 'treat':219 'unclear':193 'unit':61 'unknown':216 'usdc':14,28,55 'usdc-settlement' 'util':118 'valid':88 'wallet':183 'x':83 'x-payment':82 'x402':2,16,46,89,161 'x402 paid endpoint' 'x402-gated':1,15 'x402-payment'","prices":[{"id":"fcdb33fe-1b69-4ced-8690-eaddaabdfc5d","listingId":"c21e1605-eea5-4bf9-aea1-7745c5ebd3e9","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/15/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":"2026-04-18T18:52:12.242Z"}],"sources":[{"listingId":"c21e1605-eea5-4bf9-aea1-7745c5ebd3e9","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/portfolios/15/transactions","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:52:12.242Z","lastSeenAt":"2026-04-23T05:01:28.143Z"}],"details":{"listingId":"c21e1605-eea5-4bf9-aea1-7745c5ebd3e9","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/portfolios/15/transactions \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <x402-payment-proof>\" \\\n  -d '{}'","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 base units in USDC (USD Coin) on the Base network","source_url":"https://lowpaymentfee.com/api/v1/portfolios/15/transactions"},{"claim":"The site advertises $0.02 per request pricing with no API keys, no rate limits, and instant access on the Base network","source_url":"https://lowpaymentfee.com"},{"claim":"The USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/portfolios/15/transactions"}],"useCases":["Submitting or retrieving transactions for a portfolio via a pay-per-call model","Programmatic portfolio management without API key registration","Agent-driven financial transaction recording with instant USDC settlement"],"bestFor":["Developers wanting keyless, pay-per-use portfolio transaction access","AI agents that can settle x402 payments on Base","Users who prefer crypto micropayments over subscription billing"],"notFor":["Anyone needing documented request/response schemas before integrating","High-volume batch transaction processing where per-call fees add up","Users without USDC on the Base network"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:01.89Z"},"updatedAt":"2026-04-23T05:01:28.143Z"}}