{"id":"a358623d-b637-4e6b-90fc-0cd52399d1ee","shortId":"Vf3zqJ","kind":"x402","title":"NFT metadata endpoint on Base, pay-per-call via x402 with USDC (~$0.02/request).","tagline":"NFT metadata endpoint on Base, pay-per-call via x402 with USDC (~$0.02/request).","description":"This endpoint at lowpaymentfee.com returns NFT metadata for token ID 20 via a POST request, gated by the x402 payment protocol. The endpoint is live and returns a 402 challenge advertising payment in USDC on the Base network. The maximum amount required per call is 20,000 base units of USDC (6 decimals), which equals $0.02 USD. Payment is settled on-chain to the specified wallet address using the \"exact\" scheme.\n\nThe broader lowpaymentfee.com platform advertises a suite 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 listed at $0.02 per request with no API keys, no rate limits, and no minimum commitments. However, this specific listing covers only the `/api/v1/nfts/20/metadata` endpoint.\n\nNo OpenAPI schema, detailed documentation, or example responses were found in the crawl. The endpoint's output format is described only as `application/json`. Without sample payloads or schema definitions, the exact structure of the NFT metadata response is unknown. The platform requires an x402-compatible payment header (X-PAYMENT) to access the resource.","tags":[],"capabilities":["nft-metadata","x402-payment","usdc-base","pay-per-request","json-response"],"categories":["web3","nft"],"synonyms":["NFT metadata API","token metadata","NFT info endpoint","on-chain NFT data","x402 NFT API","Base network NFT","USDC micropayment API"],"warnings":["No OpenAPI or schema documentation available for this endpoint","No example request or response bodies found; output structure is unknown","This endpoint serves metadata for a single token ID (20); generalizability to other token IDs is unclear","The broader platform lists many endpoints but none have detailed docs in the crawl"],"endpointUrl":"https://lowpaymentfee.com/api/v1/nfts/20/metadata","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/nfts/20/metadata","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.350","qualityRationale":"The endpoint is live (402 challenge captured) and pricing is clear ($0.02 USDC on Base). However, there is no OpenAPI schema, no example request/response, and no documentation beyond the landing page listing. The specific NFT metadata content and input parameters are entirely 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'/request':15,30 '0.02':14,29,86,147 '000':77 '20':41,76 '402':59 '6':82 'Base network NFT' 'NFT info endpoint' 'NFT metadata API' 'USDC micropayment API' 'access':222 'address':98 'advertis':61,107 'ai/ml':119 'amount':71 'analysi':122 'analyt':118 'api':115,152 'application/json':192 'base':5,20,67,78 'broader':104 'call':9,24,74 'chain':93 'challeng':60 'classif':124 'commit':160 'compat':215 'convers':140 'cover':165 'crawl':182 'data':117 'decim':83 'definit':198 'describ':189 'detail':173 'document':174 'embed':125 'endpoint':3,18,32,53,143,169,184 'equal':85 'estim':134 'exact':101,200 'exampl':176 'exchang':129 'feed':128 'finance/web3':126 'format':187 'found':179 'gas':133 'gate':46 'generat':141 'geocod':138 'header':217 'howev':161 'id':40 'infer':120 'infrastructur':136 'json-response' 'key':153 'limit':156 'list':145,164 'live':55 'lowpaymentfee.com':34,105 'maximum':70 'metadata':2,17,37,205 'minimum':159 'network':68 'nft':1,16,36,204 'nft-metadata' 'on-chain':91 'on-chain NFT data' 'openapi':171 'output':186 'pay':7,22,112 'pay-per-cal':6,21 'pay-per-request':111 'payload':195 'payment':50,62,88,216,220 'per':8,23,73,113,148 'platform':106,210 'post':44 'price':127 'protocol':51 'quot':132 'rate':130,155 'request':45,114,149 'requir':72,211 'resourc':224 'respons':177,206 'return':35,57 'sampl':194 'schema':172,197 'scheme':102 'sentiment':121 'settl':90 'span':116 'specif':163 'specifi':96 'structur':201 'suit':109 'summar':123 'token':39,131 'token metadata' 'unit':79 'unknown':208 'usd':87 'usdc':13,28,64,81 'usdc-base' 'use':99 'util':137 'valid':139 'via':10,25,42 'wallet':97 'without':193 'x':219 'x-payment':218 'x402':11,26,49,214 'x402 NFT API' 'x402-compatible':213 'x402-payment'","prices":[{"id":"21a3686c-b6c3-485a-9e2a-04f9f8266e7c","listingId":"a358623d-b637-4e6b-90fc-0cd52399d1ee","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/nfts/20/metadata","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-21T18:32:27.932Z"}],"sources":[{"listingId":"a358623d-b637-4e6b-90fc-0cd52399d1ee","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/nfts/20/metadata","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:27.932Z","lastSeenAt":"2026-04-22T18:33:27.447Z"}],"details":{"listingId":"a358623d-b637-4e6b-90fc-0cd52399d1ee","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/nfts/20/metadata \\\n  -H \"X-PAYMENT: <x402-payment-token>\" \\\n  -H \"Content-Type: application/json\"","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 of USDC on Base network","source_url":"https://lowpaymentfee.com/api/v1/nfts/20/metadata"},{"claim":"All endpoints on the platform are listed at $0.02 per request with no API keys, no rate limits, and instant access","source_url":"https://lowpaymentfee.com"},{"claim":"The USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/nfts/20/metadata"}],"useCases":["Retrieving metadata for a specific NFT (token ID 20) programmatically","Integrating NFT metadata into a dApp or marketplace without managing API keys","Demonstrating x402 pay-per-call patterns for Web3 data endpoints"],"bestFor":["Agents or apps that need on-demand NFT metadata with crypto micropayments","Developers exploring x402 protocol integrations on Base","Use cases where keyless, pay-as-you-go API access is preferred"],"notFor":["Bulk retrieval of metadata across many NFT collections (only token ID 20 is served at this path)","Users who need fiat-only payment options","Applications requiring detailed OpenAPI documentation or guaranteed SLAs"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:12:58.569Z"},"updatedAt":"2026-04-22T18:33:27.447Z"}}