{"id":"23a008db-c57a-4971-93c4-273212df8faf","shortId":"tRYxrq","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 transactions API for portfolio #28, gated behind the x402 payment protocol. Each call costs up to $0.02 in USDC on the Base network (maxAmountRequired of 20,000 base units with 6 decimals). No API keys or rate limits are required — callers simply attach an X-PAYMENT header with a valid x402 payment proof to access the resource.\n\nThe hosting site (lowpaymentfee.com) advertises a broad catalog of pay-per-request APIs spanning data analytics, AI/ML inference, finance/Web3 data, and utility services, all priced at $0.02 per request and settled in USDC on Base. However, the specific endpoint being listed here — `/api/v1/portfolios/28/transactions` — is described only as \"Premium API Access\" with no further documentation on request schema, response format, or the nature of the portfolio data. The docs, pricing, and README pages on the site return only a \"Connect wallet\" prompt with no substantive content.\n\nBecause there is no OpenAPI schema, no request/response examples, and no documentation beyond the generic title, the exact functionality of this endpoint is unclear. It likely returns or creates transaction records for a portfolio, but the specifics (fields, filters, pagination) are unknown. Agents should be prepared for an opaque JSON response and may need to experiment with POST body parameters.","tags":[],"capabilities":["x402-payment","usdc-settlement","base-network","pay-per-request","portfolio-transactions","post-endpoint"],"categories":["finance","data"],"synonyms":["portfolio transactions API","x402 paid API","USDC micropayment endpoint","lowpaymentfee","pay-per-call API","Base network API","crypto payment API"],"warnings":["No OpenAPI schema or request/response documentation available","The endpoint's exact functionality (what portfolio #28 represents, what fields are accepted/returned) is unknown","All documentation pages on the site return only 'Connect wallet' with no content","The site advertises many endpoints but none have visible documentation"],"endpointUrl":"https://lowpaymentfee.com/api/v1/portfolios/28/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/28/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 (402 challenge captured) and pricing is clear ($0.02 USDC on Base), but there is no documentation, no request/response schema, and no examples. The site's docs pages are empty beyond a wallet connect prompt. This is effectively a stub 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'0.02':54,123 '000':64 '20':63 '28':42 '6':68 'Base network API' 'USDC micropayment endpoint' 'access':93,146 'advertis':100 'agent':224 'ai/ml':113 'analyt':112 'api':39,71,109,145 'attach':80 'base':8,22,37,59,65,131 'base-network' 'behind':44 'beyond':194 'bodi':240 'broad':102 'call':12,26,50 'caller':78 'catalog':103 'connect':175 'content':181 'cost':51 'creat':210 'crypto payment API' 'data':111,116,162 'decim':69 'describ':141 'doc':164 'document':150,193 'endpoint':6,20,30,135,203 'exact':199 'exampl':190 'experi':237 'expos':33 'field':219 'filter':220 'finance/web3':115 'format':155 'function':200 'gate':3,17,43 'generic':196 'header':85 'host':97 'howev':132 'infer':114 'json':231 'key':72 'like':207 'limit':75 'list':137 'lowpaymentfee' 'lowpaymentfee.com':32,99 'maxamountrequir':61 'may':234 'natur':158 'need':235 'network':60 'opaqu':230 'openapi':186 'page':168 'pagin':221 'paramet':241 'pay':10,24,106 'pay-per-cal':9,23 'pay-per-call API' 'pay-per-request':105 'payment':47,84,90 'per':11,25,107,124 'portfolio':4,18,41,161,215 'portfolio transactions API' 'portfolio-transactions' 'post':36,239 'post-bas':35 'post-endpoint' 'premium':144 'prepar':227 'price':121,165 'prompt':177 'proof':91 'protocol':48 'rate':74 'readm':167 'record':212 'request':108,125,152 'request/response':189 'requir':77 'resourc':95 'respons':154,232 'return':172,208 'schema':153,187 'servic':119 'settl':127 'simpli':79 'site':98,171 'span':110 'specif':134,218 'substant':180 'titl':197 'transact':5,19,38,211 'unclear':205 'unit':66 'unknown':223 'usdc':14,28,56,129 'usdc-settlement' 'util':118 'valid':88 'wallet':176 'x':83 'x-payment':82 'x402':2,16,46,89 'x402 paid API' 'x402-gated':1,15 'x402-payment'","prices":[{"id":"0b4ed1e3-3f23-4da4-9448-690c52133c77","listingId":"23a008db-c57a-4971-93c4-273212df8faf","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/28/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":"2026-04-18T18:52:33.913Z"}],"sources":[{"listingId":"23a008db-c57a-4971-93c4-273212df8faf","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/portfolios/28/transactions","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:52:33.913Z","lastSeenAt":"2026-04-28T03:33:43.576Z"}],"details":{"listingId":"23a008db-c57a-4971-93c4-273212df8faf","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/portfolios/28/transactions \\\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 challenge with maxAmountRequired of 20000 base units in USDC on Base network","source_url":"https://lowpaymentfee.com/api/v1/portfolios/28/transactions"},{"claim":"The site advertises $0.02 per request pricing with no API keys, no rate limits, and instant access on Base network","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base","source_url":"https://lowpaymentfee.com/api/v1/portfolios/28/transactions"}],"useCases":["Fetching or creating transaction records for a specific portfolio via a single paid API call","Integrating pay-per-request financial data into agent workflows without API key management","Demonstrating x402 protocol payment flows on Base with USDC"],"bestFor":["Developers experimenting with x402 payment protocol integrations","Agents needing keyless, pay-per-call access to portfolio transaction data","Projects that want to avoid subscription commitments for occasional API calls"],"notFor":["Users who need detailed API documentation or guaranteed schema stability","High-volume consumers who would benefit from bulk pricing or subscriptions","Anyone requiring non-crypto payment methods"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:00.871Z"},"updatedAt":"2026-04-28T03:33:43.576Z"}}