{"id":"d99a8c81-d547-4e70-a138-f497c390de74","shortId":"7JkP5Z","kind":"x402","title":"x402-gated portfolio endpoint on Base, pay $0.02 per request in USDC — no API keys required.","tagline":"x402-gated portfolio endpoint on Base, pay $0.02 per request in USDC — no API keys required.","description":"This endpoint at lowpaymentfee.com provides access to a specific portfolio resource (ID 73) via the x402 payment protocol. It is part of a broader platform that offers a variety of pay-per-call APIs spanning data analytics, AI/ML inference, finance/Web3 data, and infrastructure utilities — all gated behind x402 micropayments on the Base network using USDC.\n\nThe endpoint accepts POST requests and returns JSON. Payment is settled on-chain via USDC on Base (contract 0x8335…2913) using the \"exact\" x402 scheme. The x402 challenge advertises a maxAmountRequired of 20,000 base units; since USDC uses 6 decimals, this equals $0.02 per request, consistent with the site's advertised flat pricing. No API keys, rate limits, or upfront commitments are required — callers simply attach an X-PAYMENT header with a valid x402 payment proof.\n\nThe specific data returned by the /api/v1/portfolios/73 endpoint is not documented in the crawled material. The site's landing page groups its APIs into categories (Data & Analytics, AI & ML, Finance & Web3, Infrastructure) but does not list a \"portfolios\" category or describe the schema of portfolio responses. As a result, the exact payload structure and use case for this particular endpoint must be inferred or discovered by making a paid call. The broader platform appears to be a demonstration or marketplace of low-fee x402 endpoints.","tags":[],"capabilities":["x402-payment","usdc-base","pay-per-request","json-api","portfolio-data","no-api-key","micropayment"],"categories":["finance","data"],"synonyms":["x402 API","USDC micropayment API","Base network API","pay-per-call portfolio","lowpaymentfee","402 payment endpoint","crypto-paid API"],"warnings":["No documentation exists for the /api/v1/portfolios/73 endpoint — its response schema and purpose are unknown.","The site's docs, pricing, and README pages are empty (only show 'Connect wallet'), suggesting the platform may be early-stage or incomplete.","The 'portfolios' category is not listed among the site's advertised API groups, raising questions about whether this is a production endpoint."],"endpointUrl":"https://lowpaymentfee.com/api/v1/portfolios/73","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/73","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.350","qualityRationale":"The endpoint is live (402 challenge captured) and pricing is clear ($0.02 USDC on Base). However, there is no documentation for the /portfolios/73 resource — no request schema, no response schema, no description of what portfolio data is returned. The docs, pricing, and README pages all returned only 'Connect wallet' with no useful 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'0.02':9,26,135 '000':125 '0x8335':110 '20':124 '2913':111 '402 payment endpoint' '6':131 '73':47 'Base network API' 'USDC micropayment API' 'accept':93 'access':40 'advertis':120,143 'ai':197 'ai/ml':73 'analyt':72,196 'api':15,32,69,147,192 'appear':243 'attach':158 'base':7,24,87,108,126 'behind':82 'broader':58,241 'call':68,239 'caller':156 'case':225 'categori':194,208 'chain':104 'challeng':119 'commit':153 'consist':138 'contract':109 'crawl':183 'crypto-paid API' 'data':71,76,172,195 'decim':132 'demonstr':247 'describ':210 'discov':234 'document':180 'endpoint':5,22,36,92,177,229,255 'equal':134 'exact':114,220 'fee':253 'financ':199 'finance/web3':75 'flat':144 'gate':3,20,81 'group':190 'header':163 'id':46 'infer':74,232 'infrastructur':78,201 'json':98 'json-api' 'key':16,33,148 'land':188 'limit':150 'list':205 'low':252 'low-fe':251 'lowpaymentfee' 'lowpaymentfee.com':38 'make':236 'marketplac':249 'materi':184 'maxamountrequir':122 'micropay':84 'micropayment' 'ml':198 'must':230 'network':88 'no-api-key' 'offer':61 'on-chain':102 'page':189 'paid':238 'part':55 'particular':228 'pay':8,25,66 'pay-per-cal':65 'pay-per-call portfolio' 'pay-per-request' 'payload':221 'payment':51,99,162,168 'per':10,27,67,136 'platform':59,242 'portfolio':4,21,44,207,214 'portfolio-data' 'post':94 'price':145 'proof':169 'protocol':52 'provid':39 'rate':149 'request':11,28,95,137 'requir':17,34,155 'resourc':45 'respons':215 'result':218 'return':97,173 'schema':212 'scheme':116 'settl':101 'simpli':157 'sinc':128 'site':141,186 'span':70 'specif':43,171 'structur':222 'unit':127 'upfront':152 'usdc':13,30,90,106,129 'usdc-base' 'use':89,112,130,224 'util':79 'valid':166 'varieti':63 'via':48,105 'web3':200 'x':161 'x-payment':160 'x402':2,19,50,83,115,118,167,254 'x402 API' 'x402-gated':1,18 'x402-payment'","prices":[{"id":"9c702d04-9076-4277-ad43-512d867f09b9","listingId":"d99a8c81-d547-4e70-a138-f497c390de74","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/73","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:53:17.639Z"}],"sources":[{"listingId":"d99a8c81-d547-4e70-a138-f497c390de74","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/portfolios/73","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:53:17.639Z","lastSeenAt":"2026-04-27T18:36:24.574Z"}],"details":{"listingId":"d99a8c81-d547-4e70-a138-f497c390de74","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/portfolios/73 \\\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 in USDC on Base network","source_url":"https://lowpaymentfee.com/api/v1/portfolios/73"},{"claim":"USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base","source_url":"https://lowpaymentfee.com/api/v1/portfolios/73"},{"claim":"Platform advertises $0.02 per request flat pricing with no API keys, no rate limits, and instant access","source_url":"https://lowpaymentfee.com"},{"claim":"The site lists API categories: Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructure","source_url":"https://lowpaymentfee.com"}],"useCases":["Fetching portfolio data on-demand with per-request USDC micropayments","Agent-driven data retrieval without pre-registration or API key management","Integrating x402-compatible payment flows into automated pipelines","Exploring x402 protocol mechanics with a low-cost live endpoint"],"bestFor":["Developers experimenting with x402 payment protocol on Base","AI agents that need keyless, pay-per-call API access","Applications requiring on-chain micropayment settlement for API usage"],"notFor":["Users who need detailed, documented portfolio data schemas before purchasing","High-throughput use cases where $0.02/request adds up significantly","Anyone without a Base-compatible USDC wallet"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:58.78Z"},"updatedAt":"2026-04-27T18:36:24.574Z"}}