{"id":"63f37c01-e887-48e2-abcd-c6d536c33bc7","shortId":"TwaXR8","kind":"x402","title":"Pay-per-call premium API access on Base via x402 — $0.02/request in USDC.","tagline":"Pay-per-call premium API access on Base via x402 — $0.02/request in USDC.","description":"This endpoint at lowpaymentfee.com provides \"Premium API Access\" via the x402 payment protocol. The site hosts a broad catalog of pay-per-request 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 priced at $0.02 per request, settled in USDC on the Base network.\n\nThe specific endpoint `/api/v1/keys/63` is labeled \"Premium API Access\" and accepts POST requests. Its x402 challenge advertises a maximum amount of 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02 given USDC's 6 decimals. Payment is made via the x402 exact scheme with a 300-second timeout. No API keys or rate limits are required — callers simply attach an X-PAYMENT header with a valid x402 payment proof.\n\nDocumentation is minimal: the site's landing page lists available endpoints and pricing, but there is no OpenAPI spec, no detailed request/response schemas, and no usage examples. The `/api`, `/pricing`, and `/README` pages all resolve to a \"Connect wallet\" prompt with no additional content. Because of this, the exact functionality behind `/api/v1/keys/63` (as opposed to the other listed endpoints) is unclear — it may serve as a key-generation or access-provisioning endpoint, but this is speculative.","tags":[],"capabilities":["x402-payment","usdc-base","pay-per-request","post-method","json-response"],"categories":["api-gateway","infrastructure"],"synonyms":["x402 API","pay-per-call API","USDC micropayment API","Base network API","lowpaymentfee","premium API key","crypto-paid API"],"warnings":["No OpenAPI or schema documentation available — request and response formats are unknown.","The exact functionality of /api/v1/keys/63 ('Premium API Access') is not documented; it may differ from the other listed endpoints.","All non-root pages (/api, /pricing, /README) returned only a 'Connect wallet' prompt with no useful content.","No rate-limit or SLA information provided."],"endpointUrl":"https://lowpaymentfee.com/api/v1/keys/63","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/keys/63","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.350","qualityRationale":"The endpoint is live and returns a valid x402 402 challenge, confirming it accepts USDC payments on Base. However, there is no OpenAPI spec, no request/response schema, no usage examples, and the crawled pages beyond the landing page are empty. The exact purpose of /api/v1/keys/63 versus the other listed endpoints is 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'/api/v1/keys/63':101,223 '/pricing':201 '/readme':203 '/request':13,28 '0.02':12,27,88,131 '000':120 '0x8335':125 '20':119 '2913':126 '300':147 '6':135 'Base network API' 'USDC micropayment API' 'accept':108 'access':7,22,38,106,243 'access-provis':242 'addit':214 'advertis':114 'ai/ml':59 'amount':117 'analysi':62 'analyt':58 'api':6,21,37,55,105,151 'attach':160 'avail':181 'base':9,24,96,121,128 'behind':222 'broad':48 'call':4,19 'caller':158 'catalog':49 'challeng':113 'classif':64 'connect':209 'content':215 'convers':81 'crypto-paid API' 'data':57 'decim':136 'detail':192 'document':172 'embed':65 'endpoint':32,84,100,182,230,245 'equal':130 'estim':75 'exact':143,220 'exampl':198 'exchang':70 'feed':69 'financ':66 'function':221 'gas':74 'generat':82,240 'geocod':79 'given':132 'header':165 'host':46 'infer':60 'infrastructur':77 'json-response' 'key':152,239 'key-gener':238 'label':103 'land':178 'limit':155 'list':180,229 'lowpaymentfee' 'lowpaymentfee.com':34 'made':139 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'x402-payment'","prices":[{"id":"593ac302-13ee-4327-8316-aa777e847c12","listingId":"63f37c01-e887-48e2-abcd-c6d536c33bc7","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/keys/63","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-21T18:32:23.777Z"}],"sources":[{"listingId":"63f37c01-e887-48e2-abcd-c6d536c33bc7","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/keys/63","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:23.777Z","lastSeenAt":"2026-04-22T01:02:19.189Z"}],"details":{"listingId":"63f37c01-e887-48e2-abcd-c6d536c33bc7","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/keys/63 \\\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 site lists APIs across data & analytics, AI/ML, finance & Web3, and infrastructure categories, all priced at $0.02/request.","source_url":"https://lowpaymentfee.com"},{"claim":"Pricing is $0.02 per request with no API keys, no rate limits, instant access, on Base network.","source_url":"https://lowpaymentfee.com"},{"claim":"The x402 challenge for /api/v1/keys/63 specifies maxAmountRequired of 20000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base.","source_url":"https://lowpaymentfee.com/api/v1/keys/63"}],"useCases":["Accessing premium API services without traditional API key registration","Making one-off paid API calls settled in USDC on Base","Agent-driven programmatic access to data, AI, finance, or utility endpoints"],"bestFor":["Developers who want instant, keyless API access with crypto micropayments","AI agents that can settle x402 payments autonomously on Base","Users who prefer pay-per-use pricing with no subscriptions or commitments"],"notFor":["Users who need detailed API documentation or OpenAPI specs before integrating","Teams requiring fiat-only billing or invoicing","High-volume consumers who need bulk pricing or rate-limit guarantees"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:05.271Z"},"updatedAt":"2026-04-22T01:02:19.189Z"}}