{"id":"eaa05b50-9eab-4cea-9107-abe17c636db6","shortId":"JhkaMQ","kind":"x402","title":"x402-gated portfolio endpoint on Base, pay $0.02 per request in USDC — no API keys needed.","tagline":"x402-gated portfolio endpoint on Base, pay $0.02 per request in USDC — no API keys needed.","description":"This endpoint at lowpaymentfee.com provides premium API access to a portfolio resource (portfolio ID 16) via the x402 payment protocol. It is part of a broader platform that offers data & analytics, AI/ML inference, finance/Web3, and infrastructure utility APIs, all gated behind per-request USDC micropayments on the Base network.\n\nThe specific endpoint `/api/v1/portfolios/16` accepts POST requests and returns JSON. Payment is settled on-chain using USDC (contract 0x8335…2913 on Base) with a maximum amount of 20,000 base units, which equals $0.02 per call (USDC uses 6 decimals). The x402 challenge confirms the endpoint is live and uses the \"exact\" payment scheme with a 300-second timeout. No API keys or subscriptions are required — callers simply attach an X-PAYMENT header with a valid x402 payment proof.\n\nThe platform advertises uniform $0.02 pricing across all its endpoints, no rate limits, and instant access. However, documentation is extremely sparse: the /docs, /api, /pricing, and /README pages all render only a \"Connect wallet\" prompt with no further technical detail. There is no OpenAPI spec, no request/response schema documentation, and no explanation of what the \"portfolios\" resource actually contains or what POST body it expects. The endpoint is confirmed live (402 challenge captured), but without documentation it is difficult to know what data or functionality it provides.","tags":[],"capabilities":["x402-payment","usdc-micropayment","base-network","per-request-billing","no-api-key","json-response","portfolio-data"],"categories":["finance","data"],"synonyms":["portfolio API","x402 API","micropayment API","pay-per-call API","USDC API","Base network API","lowpaymentfee"],"warnings":["No OpenAPI or schema documentation available — request body and response format are unknown","All documentation pages (/docs, /api, /pricing, /README) render only 'Connect wallet' with no technical content","The specific data returned by /api/v1/portfolios/16 is undocumented; 'Premium API Access' is the only description","No examples of request or response payloads could be found"],"endpointUrl":"https://lowpaymentfee.com/api/v1/portfolios/16","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/16","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.300","qualityRationale":"The endpoint is confirmed live via a valid x402 402 challenge, and pricing is clear ($0.02 USDC on Base). However, there is no OpenAPI spec, no request/response schema, no documentation beyond a wallet-connect prompt, and no description of what the portfolios resource actually returns. This is effectively a stub 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'/api/v1/portfolios/16':88 '/docs':188 '/pricing':190 '/readme':192 '0.02':9,26,119,170 '000':114 '0x8335':104 '16':49 '20':113 '2913':105 '300':142 '402':236 '6':124 'Base network API' 'USDC API' 'accept':89 'access':42,181 'across':172 'actual':223 'advertis':168 'ai/ml':66 'amount':111 'analyt':65 'api':15,32,41,72,146 'attach':154 'base':7,24,83,107,115 'base-network' 'behind':75 'bodi':228 'broader':60 'call':121 'caller':152 'captur':238 'chain':100 'challeng':128,237 'confirm':129,234 'connect':198 'contain':224 'contract':103 'data':64,248 'decim':125 'detail':205 'difficult':244 'document':183,214,241 'endpoint':5,22,36,87,131,175,232 'equal':118 'exact':137 'expect':230 'explan':217 'extrem':185 'finance/web3':68 'function':250 'gate':3,20,74 'header':159 'howev':182 'id':48 'infer':67 'infrastructur':70 'instant':180 'json':94 'json-response' 'key':16,33,147 'know':246 'limit':178 'live':133,235 'lowpaymentfee' 'lowpaymentfee.com':38 'maximum':110 'micropay':80 'micropayment API' 'need':17,34 'network':84 'no-api-key' 'offer':63 'on-chain':98 'openapi':209 'page':193 'part':57 'pay':8,25 'pay-per-call API' 'payment':53,95,138,158,164 'per':10,27,77,120 'per-request':76 'per-request-billing' 'platform':61,167 'portfolio':4,21,45,47,221 'portfolio API' 'portfolio-data' 'post':90,227 'premium':40 'price':171 'prompt':200 'proof':165 'protocol':54 'provid':39,252 'rate':177 'render':195 'request':11,28,78,91 'request/response':212 'requir':151 'resourc':46,222 'return':93 'schema':213 'scheme':139 'second':143 'settl':97 'simpli':153 'spars':186 'spec':210 'specif':86 'subscript':149 'technic':204 'timeout':144 'uniform':169 'unit':116 'usdc':13,30,79,102,122 'usdc-micropayment' 'use':101,123,135 'util':71 'valid':162 'via':50 'wallet':199 'without':240 'x':157 'x-payment':156 'x402':2,19,52,127,163 'x402 API' 'x402-gated':1,18 'x402-payment'","prices":[{"id":"3be9765d-5713-45c0-857c-278574b809cb","listingId":"eaa05b50-9eab-4cea-9107-abe17c636db6","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/16","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:52:14.669Z"}],"sources":[{"listingId":"eaa05b50-9eab-4cea-9107-abe17c636db6","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/portfolios/16","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:52:14.669Z","lastSeenAt":"2026-04-28T07:34:37.731Z"}],"details":{"listingId":"eaa05b50-9eab-4cea-9107-abe17c636db6","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/portfolios/16 \\\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 x402 challenge with maxAmountRequired of 20000 base units in USDC on Base","source_url":"https://lowpaymentfee.com/api/v1/portfolios/16"},{"claim":"Platform advertises $0.02 per request, no API keys, no rate limits, 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/portfolios/16"},{"claim":"Documentation pages render only a 'Connect wallet' prompt with no further content","source_url":"https://lowpaymentfee.com/docs"}],"useCases":["Accessing portfolio data on a pay-per-request basis without managing API keys","Agent-driven workflows that need on-chain payment-gated data retrieval","Programmatic access to portfolio information settled via USDC on Base"],"bestFor":["Developers or agents wanting keyless, pay-per-call API access","Users who prefer crypto micropayments over subscription billing","x402-compatible agent toolchains on the Base network"],"notFor":["Users who need detailed API documentation or OpenAPI specs before integrating","High-volume consumers who want bulk pricing or rate-limit guarantees","Anyone without a Base-network USDC wallet or x402-compatible client"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:01.758Z"},"updatedAt":"2026-04-28T07:34:37.731Z"}}