{"id":"0f36d004-19ed-4b03-b99c-e14cb439c33a","shortId":"DREd2j","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/81/transactions`, gated by the x402 payment protocol. Each request costs up to $0.02 USDC (maxAmountRequired of 20,000 base units at 6 decimals) settled on the Base network. The endpoint accepts `application/json` and requires an `X-PAYMENT` header containing a valid x402 payment proof. No API keys or rate limits are advertised — access is granted purely through per-call micropayments.\n\nThe specific endpoint listed here is for portfolio ID 81's transactions. The broader lowpaymentfee.com platform advertises a wide catalog of x402-gated APIs spanning data analytics, AI/ML inference (sentiment, summarization, classification, embeddings), finance/crypto (price feeds, exchange rates, token quotes, gas estimates), and infrastructure utilities (geocoding, validation, conversion, generation), all at the same $0.02/request price point.\n\nDocumentation is extremely sparse. The docs, API, pricing, and README pages all render only a \"Connect wallet\" prompt with no further content. There is no OpenAPI schema, no request/response examples, and no description of what fields the transactions endpoint expects or returns. The endpoint is confirmed live (returns a proper 402 challenge), but without documentation it is difficult to know what payload to send or what data comes back.","tags":[],"capabilities":["x402-payment","usdc-base","per-call-micropayment","portfolio-transactions","post-json"],"categories":["finance","data"],"synonyms":["portfolio transactions","x402 API","micropayment API","pay-per-request","USDC gated endpoint","lowpaymentfee","Base network API"],"warnings":["No API documentation available — docs, pricing, and README pages all show only 'Connect wallet'","No OpenAPI or JSON schema describing request/response formats","The endpoint path includes a hardcoded portfolio ID (81); unclear if other IDs are accessible","Purpose and data model of 'transactions' endpoint is entirely undocumented"],"endpointUrl":"https://lowpaymentfee.com/api/v1/portfolios/81/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/81/transactions","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 with a valid 402 challenge and clear pricing ($0.02 USDC on Base). However, there is no OpenAPI schema, no request/response examples, and all documentation pages are empty beyond a wallet-connect prompt. The specific purpose of the portfolios/81/transactions endpoint is 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'/request':159 '0.02':54,158 '000':59 '20':58 '402':212 '6':63 '81':113 'Base network API' 'USDC gated endpoint' 'accept':72 'access':95 'advertis':94,120 'ai/ml':132 'analyt':131 'api':40,88,128,168 'application/json':73 'back':230 'base':8,22,37,60,68 'broader':117 'call':12,26,102 'catalog':123 'challeng':213 'classif':136 'come':229 'confirm':207 'connect':177 'contain':81 'content':183 'convers':152 'cost':51 'data':130,228 'decim':64 'descript':194 'difficult':219 'doc':167 'document':162,216 'embed':137 'endpoint':6,20,30,71,106,200,205 'estim':146 'exampl':191 'exchang':141 'expect':201 'expos':33 'extrem':164 'feed':140 'field':197 'finance/crypto':138 'gas':145 'gate':3,17,43,127 'generat':153 'geocod':150 'grant':97 'header':80 'id':112 'infer':133 'infrastructur':148 'key':89 'know':221 'limit':92 'list':107 'live':208 'lowpaymentfee' 'lowpaymentfee.com':32,118 'maxamountrequir':56 'micropay':103 'micropayment API' 'network':69 'openapi':187 'page':172 'pay':10,24 'pay-per-cal':9,23 'pay-per-request' 'payload':223 'payment':47,79,85 'per':11,25,101 'per-cal':100 'per-call-micropayment' 'platform':119 'point':161 'portfolio':4,18,38,111 'portfolio transactions' 'portfolio-transactions' 'post':36 'post-bas':35 'post-json' 'price':139,160,169 'prompt':179 'proof':86 'proper':211 'protocol':48 'pure':98 'quot':144 'rate':91,142 'readm':171 'render':174 'request':50 'request/response':190 'requir':75 'return':203,209 'schema':188 'send':225 'sentiment':134 'settl':65 'span':129 'spars':165 'specif':105 'summar':135 'token':143 'transact':5,19,39,115,199 'unit':61 'usdc':14,28,55 'usdc-base' 'util':149 'valid':83,151 'wallet':178 'wide':122 'without':215 'x':78 'x-payment':77 'x402':2,16,46,84,126 'x402 API' 'x402-gated':1,15,125 'x402-payment'","prices":[{"id":"37caf5d8-8e44-4aaa-9e08-20dc6326a0d6","listingId":"0f36d004-19ed-4b03-b99c-e14cb439c33a","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/81/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":"2026-04-18T18:53:24.860Z"}],"sources":[{"listingId":"0f36d004-19ed-4b03-b99c-e14cb439c33a","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/portfolios/81/transactions","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:53:24.860Z","lastSeenAt":"2026-04-27T17:05:05.023Z"}],"details":{"listingId":"0f36d004-19ed-4b03-b99c-e14cb439c33a","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/portfolios/81/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":"Endpoint returns 402 with x402 challenge, maxAmountRequired 20000 base units in USDC on Base","source_url":"https://lowpaymentfee.com/api/v1/portfolios/81/transactions"},{"claim":"Platform advertises $0.02/request pricing with no API keys, no rate limits, and instant access on Base network","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset contract on Base: 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/portfolios/81/transactions"}],"useCases":["Submitting or retrieving transactions for a specific portfolio via micropayment","Integrating pay-per-call financial data into agent workflows","Testing x402 payment protocol integrations against a live endpoint"],"bestFor":["Developers experimenting with x402 micropayment protocol","Agents that need keyless, pay-per-call API access on Base","Low-volume or sporadic API consumers who want no subscriptions"],"notFor":["Users needing detailed API documentation or schemas before integrating","High-volume batch processing where per-call fees add up","Anyone requiring non-crypto payment methods"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:58.415Z"},"updatedAt":"2026-04-27T17:05:05.023Z"}}