{"id":"9eb4553f-681f-4075-8b16-d3b443547783","shortId":"rZDwRg","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 provides a \"Premium API Access\" account balance lookup via the x402 payment protocol. The specific resource `/api/v1/accounts/18/balance` is accessed via HTTP POST and returns JSON. Payment is settled on the Base network using USDC (contract 0x8335…2913) with a maximum cost of 0.02 USDC per request (20,000 base units at 6 decimals).\n\nThe broader lowpaymentfee.com platform advertises a suite of pay-per-call APIs spanning data analytics, AI/ML inference (sentiment analysis, summarization, classification, embeddings), finance/Web3 (price feeds, exchange rates, token quotes, gas estimates), and infrastructure utilities (geocoding, validation, conversion, generation). All endpoints are listed at $0.02 per request with no API keys, no rate limits, and no minimum commitments. However, the specific endpoint being listed here is the account balance resource, and its exact response schema is not documented.\n\nThe x402 challenge was successfully captured (HTTP 402 with a valid accepts payload), confirming the endpoint is live. Documentation pages (/docs, /api, /pricing, /README) returned only a \"Connect wallet\" prompt with no substantive content, so details about request parameters, response format, and error handling are unknown.","tags":[],"capabilities":["x402-payment","usdc-settlement","base-network","account-balance","json-response","per-call-pricing","no-api-key"],"categories":["finance","infrastructure"],"synonyms":["account balance API","x402 API","pay-per-call API","USDC micropayment API","Base network API","lowpaymentfee","crypto payment endpoint"],"warnings":["No API documentation available — /docs, /api, /pricing, and /README all return only a 'Connect wallet' prompt with no content.","Response schema for /api/v1/accounts/18/balance is completely undocumented; the actual data returned is unknown.","The endpoint path includes a hardcoded account ID (18), suggesting it may be a single-purpose or demo resource rather than a general-purpose API.","No OpenAPI spec or machine-readable schema was found."],"endpointUrl":"https://lowpaymentfee.com/api/v1/accounts/18/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/18/balance","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.300","qualityRationale":"The x402 challenge is live and pricing is clear ($0.02 USDC per call on Base), but there is no documentation for this specific endpoint's request parameters or response schema. All doc pages returned only 'Connect wallet' with no content. The endpoint's purpose ('account balance') is vague with no 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'/api/v1/accounts/18/balance':49 '/docs':184 '/pricing':186 '/readme':187 '0.02':75,130 '000':80 '0x8335':68 '20':79 '2913':69 '402':171 '6':84 'Base network API' 'USDC micropayment API' 'accept':175 'access':37,51 'account':4,18,38,153 'account balance API' 'account-balance' 'advertis':90 'ai/ml':102 'analysi':105 'analyt':101 'api':36,98,135 'balanc':5,19,39,154 'base':8,22,63,81 'base-network' 'broader':87 'call':12,26,97 'captur':169 'challeng':166 'classif':107 'commit':143 'confirm':177 'connect':191 'content':197 'contract':67 'convers':123 'cost':73 'crypto payment endpoint' 'data':100 'decim':85 'detail':199 'document':163,182 'embed':108 'endpoint':6,20,30,126,147,179 'error':206 'estim':117 'exact':158 'exchang':112 'feed':111 'finance/web3':109 'format':204 'gas':116 'gate':3,17 'generat':124 'geocod':121 'handl':207 'howev':144 'http':53,170 'infer':103 'infrastructur':119 'json':57 'json-response' 'key':136 'limit':139 'list':128,149 'live':181 'lookup':40 'lowpaymentfee' 'lowpaymentfee.com':32,88 'maximum':72 'minimum':142 'network':64 'no-api-key' 'page':183 'paid':9,23 'paramet':202 'pay':95 'pay-per-cal':94 'pay-per-call API' 'payload':176 'payment':44,58 'per':11,25,77,96,131 'per-cal':10,24 'per-call-pricing' 'platform':89 'post':54 'premium':35 'price':110 'prompt':193 'protocol':45 'provid':33 'quot':115 'rate':113,138 'request':78,132,201 'resourc':48,155 'respons':159,203 'return':56,188 'schema':160 'sentiment':104 'settl':60 'span':99 'specif':47,146 'substant':196 'success':168 'suit':92 'summar':106 'token':114 'unit':82 'unknown':209 'usdc':14,28,66,76 'usdc-settlement' 'use':65 'util':120 'valid':122,174 'via':41,52 'wallet':192 'x402':2,16,43,165 'x402 API' 'x402-gated':1,15 'x402-payment'","prices":[{"id":"1c5491c9-ddbe-4be6-9522-339c0baf2c51","listingId":"9eb4553f-681f-4075-8b16-d3b443547783","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/18/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":"2026-04-18T18:39:20.245Z"}],"sources":[{"listingId":"9eb4553f-681f-4075-8b16-d3b443547783","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/accounts/18/balance","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-18T18:39:20.245Z","lastSeenAt":"2026-04-30T13:33:45.117Z"}],"details":{"listingId":"9eb4553f-681f-4075-8b16-d3b443547783","quickStartSnippet":"# The endpoint requires an x402 payment header (USDC on Base).\n# First, send a POST to discover the 402 challenge:\ncurl -X POST https://lowpaymentfee.com/api/v1/accounts/18/balance\n# Returns 402 with x402 accepts payload.\n# Then attach a valid X-PAYMENT header with a signed USDC payment.","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 x402Version 1, accepting USDC on Base with maxAmountRequired of 20000 base units","source_url":"https://lowpaymentfee.com/api/v1/accounts/18/balance"},{"claim":"USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base","source_url":"https://lowpaymentfee.com/api/v1/accounts/18/balance"},{"claim":"All APIs listed at $0.02 per request with no API keys, no rate limits, and instant access on Base network","source_url":"https://lowpaymentfee.com"},{"claim":"Platform offers APIs across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories","source_url":"https://lowpaymentfee.com"}],"useCases":["Querying account balance information via a single paid API call","Integrating pay-per-request balance lookups into agent workflows","Demonstrating x402 payment protocol integration on Base"],"bestFor":["Developers experimenting with x402 payment protocol","Agents needing on-demand account balance data without API key management","Low-volume, pay-as-you-go API consumption"],"notFor":["High-volume balance queries where per-call fees add up","Users who need detailed API documentation or guaranteed SLAs","Production systems requiring well-documented response schemas"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:14:39.216Z"},"updatedAt":"2026-04-30T13:33:45.117Z"}}