{"id":"2626ef4a-5f0b-4bfc-acfb-2bff10caa35c","shortId":"mrE8rZ","kind":"x402","title":"Retrieve email attachments via x402 micropayment on Base for $0.02 per request.","tagline":"Retrieve email attachments via x402 micropayment on Base for $0.02 per request.","description":"This endpoint at lowpaymentfee.com provides access to email attachments (specifically email ID 19) behind an x402 paywall. The endpoint accepts POST requests and returns JSON. Payment is settled on the Base network using USDC (USD Coin) at a cost of $0.02 per request (20,000 base units with 6 decimals). No API keys or rate limits are required — callers simply include an X-PAYMENT header with a valid x402 payment proof.\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 data (price feeds, exchange rates, token quotes, gas estimates), and infrastructure utilities (geocoding, validation, conversion, generation). All endpoints share the same $0.02/request pricing model and x402 payment flow on Base.\n\nDocumentation is extremely sparse — the docs, API, pricing, and README pages all render only a \"Connect wallet\" prompt with no further technical detail. There is no OpenAPI spec, no request/response schema documentation, and no usage examples available. The specific purpose and payload format of the `/api/v1/emails/19/attachments` endpoint is unclear beyond its path semantics. The endpoint is confirmed live (returns a proper 402 challenge).","tags":[],"capabilities":["x402-payment","email-attachments","usdc-base","pay-per-request","no-api-key","json-response"],"categories":["data","email"],"synonyms":["email attachment API","x402 email endpoint","micropayment email API","Base USDC API","pay-per-call email","lowpaymentfee API"],"warnings":["No OpenAPI spec or schema documentation available","Docs, API, pricing, and README pages all render only 'Connect wallet' with no content","The purpose and expected request body for /api/v1/emails/19/attachments is undocumented","No example requests or responses available anywhere in crawled material","Endpoint path references a hardcoded email ID (19), suggesting limited or demo functionality"],"endpointUrl":"https://lowpaymentfee.com/api/v1/emails/19/attachments","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/emails/19/attachments","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}]},"qualityScore":"0.250","qualityRationale":"The endpoint is live and returns a valid x402 402 challenge, confirming pricing and network. However, there is no OpenAPI spec, no request/response schema, no documentation beyond a wallet-connect prompt, and no examples. The specific functionality of this email attachments endpoint is unclear. This is effectively a stub 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'/request':143 '0.02':10,22,65,142 '000':69 '19':37 '20':68 '402':213 '6':73 'Base USDC API' 'accept':44 'access':30 'advertis':101 'ai/ml':113 'analysi':116 'analyt':112 'api':76,109,158 'attach':3,15,33 'avail':188 'base':8,20,55,70,151 'behind':38 'beyond':201 'broader':98 'call':108 'caller':83 'challeng':214 'classif':118 'coin':60 'confirm':208 'connect':167 'convers':135 'cost':63 'data':111,121 'decim':74 'detail':174 'doc':157 'document':152,183 'email':2,14,32,35 'email attachment API' 'email-attachments' 'embed':119 'endpoint':26,43,138,198,206 'estim':129 'exampl':187 'exchang':124 'extrem':154 'feed':123 'finance/web3':120 'flow':149 'format':194 'gas':128 'generat':136 'geocod':133 'header':90 'id':36 'includ':85 'infer':114 'infrastructur':131 'json':49 'json-response' 'key':77 'limit':80 'live':209 'lowpaymentfee API' 'lowpaymentfee.com':28,99 'micropay':6,18 'micropayment email API' 'model':145 'network':56 'no-api-key' 'openapi':178 'page':162 'path':203 'pay':106 'pay-per-cal':105 'pay-per-call email' 'pay-per-request' 'payload':193 'payment':50,89,95,148 'paywal':41 'per':11,23,66,107 'platform':100 'post':45 'price':122,144,159 'prompt':169 'proof':96 'proper':212 'provid':29 'purpos':191 'quot':127 'rate':79,125 'readm':161 'render':164 'request':12,24,46,67 'request/response':181 'requir':82 'retriev':1,13 'return':48,210 'schema':182 'semant':204 'sentiment':115 'settl':52 'share':139 'simpli':84 'span':110 'spars':155 'spec':179 'specif':34,190 'suit':103 'summar':117 'technic':173 'token':126 'unclear':200 'unit':71 'usag':186 'usd':59 'usdc':58 'usdc-base' 'use':57 'util':132 'valid':93,134 'via':4,16 'wallet':168 'x':88 'x-payment':87 'x402':5,17,40,94,147 'x402 email endpoint' 'x402-payment'","prices":[{"id":"d85d9946-2788-4611-8a67-4579b7e76fd5","listingId":"2626ef4a-5f0b-4bfc-acfb-2bff10caa35c","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/emails/19/attachments","description":"Premium API Access","outputSchema":{"input":{"type":"http","method":"GET","discoverable":true}},"maxAmountRequired":"20000","maxTimeoutSeconds":300}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-21T18:32:10.931Z"}],"sources":[{"listingId":"2626ef4a-5f0b-4bfc-acfb-2bff10caa35c","source":"x402_bazaar","sourceId":"https://lowpaymentfee.com/api/v1/emails/19/attachments","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:10.931Z","lastSeenAt":"2026-04-22T10:32:39.118Z"}],"details":{"listingId":"2626ef4a-5f0b-4bfc-acfb-2bff10caa35c","quickStartSnippet":"curl -X POST https://lowpaymentfee.com/api/v1/emails/19/attachments \\\n  -H \"X-PAYMENT: <x402-payment-proof>\" \\\n  -H \"Content-Type: application/json\"","exampleRequest":null,"exampleResponse":null,"schema":{"input":{"type":"http","method":"GET","discoverable":true}},"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"Endpoint returns a valid x402 402 challenge with maxAmountRequired of 20000 in USDC on Base","source_url":"https://lowpaymentfee.com/api/v1/emails/19/attachments"},{"claim":"Platform advertises $0.02/request pricing with no API keys, no rate limits, and instant access on Base network","source_url":"https://lowpaymentfee.com"},{"claim":"USDC asset contract on Base: 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","source_url":"https://lowpaymentfee.com/api/v1/emails/19/attachments"},{"claim":"Docs, API, pricing, and README pages show only 'Connect wallet'","source_url":"https://lowpaymentfee.com/docs"}],"useCases":["Retrieving email attachments programmatically via micropayment","Agent-driven email data access without API key management","Paying per-request for email content on Base network"],"bestFor":["Agents that need on-demand email attachment retrieval with crypto micropayments","Developers exploring x402 payment protocol integrations","Use cases requiring keyless, pay-as-you-go API access"],"notFor":["Bulk email processing requiring high throughput at low cost","Users who need detailed API documentation or SDKs before integrating","Non-crypto workflows that cannot settle payments on Base"],"kindDetails":{"x402_version":1,"resource_type":"http","bazaar_last_updated":"2026-02-17T23:13:21.597Z"},"updatedAt":"2026-04-22T10:32:39.118Z"}}