{"id":"b66660f1-2ece-4e53-9afb-3f90262c42a9","shortId":"tvbmjr","kind":"x402","title":"x402-gated account balance endpoint on Base, paid per-call in USDC.","tagline":"x402-gated account balance endpoint on Base, paid per-call in USDC.","description":"This endpoint at lowpaymentfee.com exposes an account balance lookup at `/api/v1/accounts/21/balance` behind an x402 paywall. It accepts POST requests and returns JSON. Payment is settled on the Base network using USDC (contract 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) with a maximum cost of $0.02 per request (20,000 base units at 6 decimals). No API keys or rate limits are required — callers simply attach an X-PAYMENT header with a valid x402 payment proof.\n\nThe provider, lowpaymentfee.com, hosts a broader catalog of x402-gated APIs spanning data analytics, AI/ML inference (sentiment analysis, summarization, classification, embeddings), finance/crypto market data, and utility services (geocoding, validation, conversion, generation), all priced at $0.02 per request. However, this specific listing covers only the `/api/v1/accounts/21/balance` endpoint. The exact response schema and the meaning of \"account 21\" are not documented in the crawled material.\n\nThe endpoint is confirmed live: the probe received a proper HTTP 402 challenge with x402 version 1 headers. Documentation pages (/docs, /pricing, /api, /README) all returned only a \"Connect wallet\" prompt with no substantive content, so details about request parameters, response fields, and error handling are unknown.","tags":[],"capabilities":["x402-payment","usdc-base","account-balance","per-call-pricing","no-api-key","json-response"],"categories":["finance","data"],"synonyms":["account balance API","x402 balance endpoint","USDC micropayment API","Base network API","pay-per-call balance","lowpaymentfee"],"warnings":["No documentation available — /docs, /pricing, /api, and /README all return only a 'Connect wallet' prompt with no content.","The meaning of 'accounts/21/balance' is unexplained; it is unclear what account 21 refers to or what the response contains.","No request body schema or response schema is provided anywhere in the crawled material.","The broader site advertises many endpoints but none have documented behavior beyond a title and price."],"endpointUrl":"https://lowpaymentfee.com/api/v1/accounts/21/balance","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/accounts/21/balance","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, but there is no documentation, no request/response schema, and no explanation of what 'accounts/21/balance' actually returns. All doc pages render only a wallet-connect prompt. The listing is essentially a 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'/api/v1/accounts/21/balance':39,144 '/docs':183 '/pricing':184 '/readme':186 '0.02':67,134 '000':71 '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913':61 '1':179 '20':70 '21':155 '402':174 '6':75 'Base network API' 'USDC micropayment API' 'accept':45 'account':4,18,35,154 'account balance API' 'account-balance' 'ai/ml':114 'analysi':117 'analyt':113 'api':78,110 'attach':87 'balanc':5,19,36 'base':8,22,56,72 'behind':40 'broader':104 'call':12,26 'caller':85 'catalog':105 'challeng':175 'classif':119 'confirm':166 'connect':191 'content':197 'contract':60 'convers':129 'cost':65 'cover':141 'crawl':161 'data':112,123 'decim':76 'detail':199 'document':158,181 'embed':120 'endpoint':6,20,30,145,164 'error':206 'exact':147 'expos':33 'field':204 'finance/crypto':121 'gate':3,17,109 'generat':130 'geocod':127 'handl':207 'header':92,180 'host':102 'howev':137 'http':173 'infer':115 'json':50 'json-response' 'key':79 'limit':82 'list':140 'live':167 'lookup':37 'lowpaymentfee' 'lowpaymentfee.com':32,101 'market':122 'materi':162 'maximum':64 'mean':152 'network':57 'no-api-key' 'page':182 'paid':9,23 'paramet':202 'pay-per-call balance' 'payment':51,91,97 'paywal':43 'per':11,25,68,135 'per-cal':10,24 'per-call-pricing' 'post':46 'price':132 'probe':169 'prompt':193 'proof':98 'proper':172 'provid':100 'rate':81 'receiv':170 'request':47,69,136,201 'requir':84 'respons':148,203 'return':49,188 'schema':149 'sentiment':116 'servic':126 'settl':53 'simpli':86 'span':111 'specif':139 'substant':196 'summar':118 'unit':73 'unknown':209 'usdc':14,28,59 'usdc-base' 'use':58 'util':125 'valid':95,128 'version':178 'wallet':192 'x':90 'x-payment':89 'x402':2,16,42,96,108,177 'x402 balance endpoint' 'x402-gated':1,15,107 'x402-payment'","prices":[{"id":"70502625-49f1-4b81-876f-1422f37d3c23","listingId":"b66660f1-2ece-4e53-9afb-3f90262c42a9","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/accounts/21/balance","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-18T18:39:22.703Z"}],"sources":[{"listingId":"b66660f1-2ece-4e53-9afb-3f90262c42a9","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/accounts/21/balance","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:39:22.703Z","lastSeenAt":"2026-04-29T06:33:42.098Z"}],"details":{"listingId":"b66660f1-2ece-4e53-9afb-3f90262c42a9","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/accounts/21/balance \\\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":"Endpoint returns HTTP 402 with x402 version 1 challenge on Base network using USDC","source_url":"https://lowpaymentfee.com/api/v1/accounts/21/balance"},{"claim":"maxAmountRequired is 20000 base units of USDC (6 decimals = $0.02)","source_url":"https://lowpaymentfee.com/api/v1/accounts/21/balance"},{"claim":"Site advertises $0.02/request pricing with no API keys, no rate limits, and instant access","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base","source_url":"https://lowpaymentfee.com/api/v1/accounts/21/balance"}],"useCases":["Querying account balance data via a single paid API call","Agent-driven balance lookups without pre-registration or API keys","Programmatic access to account information settled in USDC on Base"],"bestFor":["AI agents that need keyless, pay-per-call API access","Developers experimenting with x402 payment protocol integrations","Scenarios requiring low-friction, no-subscription data access"],"notFor":["High-volume balance polling where $0.02/request adds up quickly","Users who need detailed documentation or guaranteed SLAs before integrating"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:39.096Z"},"updatedAt":"2026-04-29T06:33:42.098Z"}}