{"id":"c427feb6-130a-48f1-8f46-ec3ee2e53741","shortId":"Br5e9z","kind":"x402","title":"Retrieve portfolio holdings via x402 micropayment on Base for $0.02 per request.","tagline":"Retrieve portfolio holdings via x402 micropayment on Base for $0.02 per request.","description":"This endpoint at lowpaymentfee.com returns holdings data for portfolio #52 via a POST request, gated by the x402 payment protocol. Each call costs $0.02 in USDC on the Base network — the x402 challenge advertises a maxAmountRequired of 20,000 base units of USDC (6 decimals), which equals $0.02. No API keys or rate limits are required; callers simply attach an X-PAYMENT header with a valid x402 payment proof.\n\nThe provider site (lowpaymentfee.com) hosts a broader catalog of pay-per-call APIs spanning data analytics, AI/ML inference, finance/crypto market data, and utility services, all priced at $0.02 per request on the Base network. This specific endpoint sits under the Finance & Web3 category and appears to serve portfolio-level holdings information, though the exact response schema is not documented.\n\nBecause the crawled documentation pages (docs, pricing, README) all resolve to a minimal \"Connect wallet\" prompt with no further content, there is no published OpenAPI spec, no response schema, and no example payloads available. The endpoint is confirmed live (402 challenge captured), but the lack of documentation means callers must discover the request/response format experimentally.","tags":[],"capabilities":["x402-payment","portfolio-holdings","usdc-base","pay-per-call","no-api-key","no-rate-limit"],"categories":["finance","data"],"synonyms":["portfolio holdings API","investment holdings","x402 finance API","crypto portfolio data","Base USDC micropayment API","lowpaymentfee","pay-per-request holdings"],"warnings":["No OpenAPI or response schema available — request/response format is undocumented","All documentation pages (/docs, /pricing, /README) return only a 'Connect wallet' prompt with no content","The specific meaning of portfolio #52 is not explained anywhere in the crawled material","No examples of successful responses are available"],"endpointUrl":"https://lowpaymentfee.com/api/v1/portfolios/52/holdings","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/52/holdings","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.350","qualityRationale":"The endpoint is confirmed live with a valid x402 402 challenge, and pricing is clear ($0.02 USDC on Base). However, there is no OpenAPI spec, no response schema, no request body documentation, and all doc pages are empty stubs. The purpose of 'portfolio 52 holdings' is unexplained. This is effectively a stub 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'000':63 '20':62 '402':195 '52':34 '6':68 'Base USDC micropayment API' 'advertis':58 'ai/ml':112 'analyt':111 'api':74,108 'appear':140 'attach':83 'avail':189 'base':8,20,53,64,128 'broader':101 'call':46,107 'caller':81,204 'captur':197 'catalog':102 'categori':138 'challeng':57,196 'confirm':193 'connect':169 'content':175 'cost':47 'crawl':158 'crypto portfolio data' 'data':31,110,116 'decim':69 'discov':206 'doc':161 'document':155,159,202 'endpoint':26,132,191 'equal':71 'exact':150 'exampl':187 'experiment':210 'financ':136 'finance/crypto':114 'format':209 'gate':39 'header':88 'hold':3,15,30,146 'host':99 'infer':113 'inform':147 'investment holdings' 'key':75 'lack':200 'level':145 'limit':78 'live':194 'lowpaymentfee' 'lowpaymentfee.com':28,98 'market':115 'maxamountrequir':60 'mean':203 'micropay':6,18 'minim':168 'must':205 'network':54,129 'no-api-key' 'no-rate-limit' 'openapi':180 'page':160 'pay':105 'pay-per-cal':104 'pay-per-call' 'pay-per-request holdings' 'payload':188 'payment':43,87,93 'per':11,23,106,124 'portfolio':2,14,33,144 'portfolio holdings API' 'portfolio-holdings' 'portfolio-level':143 'post':37 'price':121,162 'prompt':171 'proof':94 'protocol':44 'provid':96 'publish':179 'rate':77 'readm':163 'request':12,24,38,125 'request/response':208 'requir':80 'resolv':165 'respons':151,183 'retriev':1,13 'return':29 'schema':152,184 'serv':142 'servic':119 'simpli':82 'sit':133 'site':97 'span':109 'spec':181 'specif':131 'though':148 'unit':65 'usdc':50,67 'usdc-base' 'util':118 'valid':91 'via':4,16,35 'wallet':170 'web3':137 'x':86 'x-payment':85 'x402':5,17,42,56,92 'x402 finance API' 'x402-payment'","prices":[{"id":"0b1046a2-393f-4729-bab7-86b323121a7e","listingId":"c427feb6-130a-48f1-8f46-ec3ee2e53741","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/52/holdings","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:52:53.647Z"}],"sources":[{"listingId":"c427feb6-130a-48f1-8f46-ec3ee2e53741","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/portfolios/52/holdings","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:52:53.647Z","lastSeenAt":"2026-04-27T22:33:21.131Z"}],"details":{"listingId":"c427feb6-130a-48f1-8f46-ec3ee2e53741","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/portfolios/52/holdings \\\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 advertises maxAmountRequired of 20000 base units of USDC on Base network","source_url":"https://lowpaymentfee.com/api/v1/portfolios/52/holdings"},{"claim":"USDC asset contract on Base: 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/portfolios/52/holdings"},{"claim":"All APIs priced at $0.02 per request with no API keys, no rate limits, instant access on Base network","source_url":"https://lowpaymentfee.com"},{"claim":"The site lists Finance & Web3, Data & Analytics, AI & ML, and Infrastructure API categories","source_url":"https://lowpaymentfee.com"}],"useCases":["Fetching current holdings for a specific portfolio programmatically","Integrating portfolio data into trading bots or dashboards","Agent-driven portfolio monitoring with per-call micropayments"],"bestFor":["Developers wanting keyless, pay-per-call access to portfolio data","AI agents that can settle x402 payments on Base","Low-volume or sporadic portfolio data lookups without subscription commitments"],"notFor":["High-frequency bulk data retrieval where per-call costs add up","Users who need detailed API documentation or guaranteed SLAs before integrating"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:59.94Z"},"updatedAt":"2026-04-27T22:33:21.131Z"}}