x402-gated premium API access on Base, pay $0.02 per request in USDC — no API keys required.
What it does
lowpaymentfee.com offers a suite of pay-per-call API endpoints gated by the x402 protocol on the Base network. The specific endpoint `/api/v1/cards/6` is listed as "Premium API Access" and returns a 402 challenge requesting payment in USDC (contract 0x8335…2913 on Base). The maximum amount required per call is 20,000 base units of USDC (6 decimals), which equals $0.02 USD. Payment is made via the x402 exact scheme with no API keys, subscriptions, or rate limits advertised.
The broader lowpaymentfee.com platform advertises endpoints across four categories: Data & Analytics (metrics, reports, data export, insights), AI & Machine Learning (sentiment analysis, text summarization, classification, embeddings), Finance & Web3 (price feeds, exchange rates, token quotes, gas estimates), and Infrastructure (geocoding, validation, conversion, generation). All endpoints are listed at the same $0.02/request price point. However, the `/api/v1/cards/6` endpoint does not clearly map to any of these named categories, and its specific functionality beyond "Premium API Access" is undocumented.
Documentation is extremely sparse — the /docs, /api, /pricing, and /README pages all render only a "Connect wallet" prompt with no further content. There is no OpenAPI spec, no request/response schema, and no usage examples available. The endpoint is confirmed live (402 challenge captured), but without documentation it is unclear what data or service this specific endpoint returns.
Capabilities
Use cases
- —Accessing premium data or services with per-request USDC micropayments on Base
- —Agent-driven API consumption without pre-registration or API key management
- —Programmatic pay-as-you-go access to undocumented premium content
Fit
Best for
- —Developers wanting zero-signup, pay-per-call API access
- —AI agents with x402 payment capability on Base
- —Users who prefer crypto micropayments over subscription billing
Not for
- —Users who need detailed API documentation or response schemas before integrating
- —Anyone without a Base-compatible USDC wallet
- —High-volume consumers who need bulk pricing or rate guarantees
Quick start
# The endpoint requires an x402 payment header (USDC on Base).
# 1. Send POST to get the 402 challenge:
curl -X POST https://lowpaymentfee.com/api/v1/cards/6
# 2. Parse the 402 JSON, construct an x402 payment proof for 20000 base units ($0.02 USDC),
# then resend with the X-PAYMENT header:
curl -X POST https://lowpaymentfee.com/api/v1/cards/6 \
-H "X-PAYMENT: <signed-payment-payload>"Endpoint
Quality
The endpoint is confirmed live with a valid 402 challenge, but there is zero documentation on what it actually returns. No OpenAPI spec, no request/response schema, no examples. The endpoint name 'cards/6' and description 'Premium API Access' are opaque. Score reflects a live but essentially undocumented stub.
Warnings
- —No documentation available — /docs, /api, /pricing, and /README pages all show only 'Connect wallet' with no content.
- —The specific function of /api/v1/cards/6 ('Premium API Access') is completely undocumented; it does not map to any named endpoint on the landing page.
- —No request body schema or response schema is provided; integrators cannot know what to send or what to expect back.
- —No OpenAPI or machine-readable spec is available.
Citations
- —The endpoint returns a 402 challenge requesting 20000 base units of USDC on Base (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913).https://lowpaymentfee.com/api/v1/cards/6
- —All listed endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant access on Base network.https://lowpaymentfee.com
- —The platform offers endpoints in Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructure categories.https://lowpaymentfee.com
- —Documentation pages (/docs, /api, /pricing, /README) render only a 'Connect wallet' prompt with no further content.https://lowpaymentfee.com/docs