{"id":"0adc03d4-b879-4649-b980-36613f48c5ba","shortId":"hS67jq","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 provides access to portfolio transaction data via a POST request to `/api/v1/portfolios/40/transactions`. It is part of a broader platform (lowpaymentfee.com) that offers a variety of pay-per-request APIs spanning data analytics, AI/ML inference, finance/Web3 data, and utility services — all gated behind the x402 payment protocol on the Base network.\n\nThe specific endpoint probed here returns an x402 challenge requesting payment in USDC (contract `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913` on Base). The `maxAmountRequired` is 20,000 base units, which at 6 decimals for USDC equals $0.02 per request. Payment is made via the x402 `exact` scheme, with a 300-second timeout. No API keys or rate limits are advertised; access is granted purely through per-call micropayment.\n\nDocumentation on the site is extremely sparse — the docs, pricing, API, and README pages all render only a \"Connect wallet\" prompt with no substantive content. There is no OpenAPI schema, no request/response examples, and no description of what fields the transactions endpoint accepts or returns. The endpoint name suggests it retrieves or creates transactions for a specific portfolio (ID 40), but the exact semantics, required POST body, and response format are unknown. The platform's landing page lists many other endpoints at $0.02 each across categories like sentiment analysis, text summarization, geocoding, and crypto gas estimates, but none have documented schemas either.","tags":[],"capabilities":["x402-payment","usdc-micropayment","base-network","portfolio-transactions","pay-per-request","no-api-key"],"categories":["finance","data"],"synonyms":["portfolio transactions API","x402 paid API","USDC micropayment API","lowpaymentfee","Base network API","pay-per-call API","crypto payment API"],"warnings":["No OpenAPI schema or request/response documentation available","Docs, pricing, API, and README pages all render only 'Connect wallet' with no content","The specific purpose and accepted POST body for /api/v1/portfolios/40/transactions is undocumented","Portfolio ID 40 is hardcoded in the URL — unclear if other portfolio IDs are available or what this portfolio represents","The broader platform lists many endpoints but none appear to have documented schemas"],"endpointUrl":"https://lowpaymentfee.com/api/v1/portfolios/40/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/40/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 and returns a valid x402 challenge with clear pricing ($0.02 USDC on Base). However, there is no OpenAPI schema, no request/response documentation, no examples, and the docs pages are empty. The purpose of this specific endpoint (portfolios/40/transactions) is unclear beyond the name. This is effectively a stub 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'0.02':115,230 '000':105 '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913':98 '20':104 '300':128 '40':207 '6':110 'Base network API' 'USDC micropayment API' 'accept':190 'access':34,139 'across':232 'advertis':138 'ai/ml':66 'analysi':236 'analyt':65 'api':62,132,158 'base':8,22,82,100,106 'base-network' 'behind':75 'bodi':214 'broader':50 'call':12,26,146 'categori':233 'challeng':92 'connect':166 'content':172 'contract':97 'creat':200 'crypto':241 'crypto payment API' 'data':38,64,69 'decim':111 'descript':183 'doc':156 'document':148,247 'either':249 'endpoint':6,20,30,86,189,194,228 'equal':114 'estim':243 'exact':124,210 'exampl':180 'extrem':153 'field':186 'finance/web3':68 'format':217 'gas':242 'gate':3,17,74 'geocod':239 'grant':141 'id':206 'infer':67 'key':133 'land':223 'like':234 'limit':136 'list':225 'lowpaymentfee' 'lowpaymentfee.com':32,52 'made':120 'mani':226 'maxamountrequir':102 'micropay':147 'name':195 'network':83 'no-api-key' 'none':245 'offer':54 'openapi':176 'page':161,224 'part':47 'pay':10,24,59 'pay-per-cal':9,23 'pay-per-call API' 'pay-per-request':58 'payment':78,94,118 'per':11,25,60,116,145 'per-cal':144 'platform':51,221 'portfolio':4,18,36,205 'portfolio transactions API' 'portfolio-transactions' 'post':41,213 'price':157 'probe':87 'prompt':168 'protocol':79 'provid':33 'pure':142 'rate':135 'readm':160 'render':163 'request':42,61,93,117 'request/response':179 'requir':212 'respons':216 'retriev':198 'return':89,192 'schema':177,248 'scheme':125 'second':129 'semant':211 'sentiment':235 'servic':72 'site':151 'span':63 'spars':154 'specif':85,204 'substant':171 'suggest':196 'summar':238 'text':237 'timeout':130 'transact':5,19,37,188,201 'unit':107 'unknown':219 'usdc':14,28,96,113 'usdc-micropayment' 'util':71 'varieti':56 'via':39,121 'wallet':167 'x402':2,16,77,91,123 'x402 paid API' 'x402-gated':1,15 'x402-payment'","prices":[{"id":"c949813c-b716-4e8a-9997-0502c8dcbb53","listingId":"0adc03d4-b879-4649-b980-36613f48c5ba","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/40/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":"2026-04-18T18:52:46.490Z"}],"sources":[{"listingId":"0adc03d4-b879-4649-b980-36613f48c5ba","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/portfolios/40/transactions","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:52:46.490Z","lastSeenAt":"2026-04-27T22:33:20.902Z"}],"details":{"listingId":"0adc03d4-b879-4649-b980-36613f48c5ba","quickStartSnippet":"# x402 endpoint — send a POST with X-PAYMENT header containing a valid x402 payment proof\ncurl -X POST https://lowpaymentfee.com/api/v1/portfolios/40/transactions \\\n  -H \"Content-Type: application/json\" \\\n  -H \"X-PAYMENT: <x402_payment_token>\"","exampleRequest":null,"exampleResponse":null,"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"The endpoint returns an x402 challenge with maxAmountRequired of 20000 base units in USDC on Base network","source_url":"https://lowpaymentfee.com/api/v1/portfolios/40/transactions"},{"claim":"USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base","source_url":"https://lowpaymentfee.com/api/v1/portfolios/40/transactions"},{"claim":"Platform advertises $0.02 per request, no API keys, no rate limits, instant access on Base network","source_url":"https://lowpaymentfee.com"},{"claim":"Docs, pricing, API, and README pages render only 'Connect wallet' with no documentation content","source_url":"https://lowpaymentfee.com/docs"}],"useCases":["Retrieving or posting portfolio transaction records via micropayment","Integrating pay-per-call financial data into agent workflows","Accessing portfolio data without API key registration"],"bestFor":["Agents or developers who want keyless, pay-per-request access to portfolio transaction data","x402-compatible clients on the Base network","Low-volume or exploratory use where per-call pricing is preferred over subscriptions"],"notFor":["Users who need well-documented API schemas and response formats before integrating","High-volume consumers who would benefit from bulk pricing or subscriptions","Anyone requiring non-USDC or non-Base-network payment options"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:00.203Z"},"updatedAt":"2026-04-27T22:33:20.902Z"}}