x402-gated API platform on Base offering data, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402 protocol API marketplace that gates access to a variety of endpoints behind per-request micropayments settled in USDC on the Base network. The specific endpoint at `/api/v1/carts/19` is listed as "Premium API Access" and costs up to $0.02 per call (20,000 base units of USDC with 6 decimals). Payment is handled via the x402 exact scheme — callers include an X-PAYMENT header with a signed payment to the provider's address, and the endpoint returns JSON.
The broader platform advertises four categories of APIs: 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 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 required.
Note that the specific endpoint `/api/v1/carts/19` does not clearly map to any of the documented API categories — it appears to be a cart resource, which is not described on the landing page. Documentation pages (docs, pricing, README) returned only a "Connect wallet" prompt with no substantive content, so details about request/response schemas, authentication flows, or the actual functionality behind this particular endpoint are unknown.
Capabilities
Use cases
- —Programmatic access to pay-per-call API endpoints without traditional API key management
- —Agent-driven workflows that need to purchase API access on-the-fly via x402 micropayments
- —Accessing data, AI inference, finance, or utility services with per-request billing on Base
Fit
Best for
- —Developers or agents wanting zero-commitment, pay-as-you-go API access
- —x402-compatible agents that can sign USDC payments on Base
- —Use cases requiring no rate limits and instant access without signup
Not for
- —Users who need detailed API documentation or well-defined schemas before integrating
- —High-volume consumers who would benefit from bulk pricing or subscription plans
- —Anyone without a Base-compatible USDC wallet
Quick start
# The endpoint requires an X-PAYMENT header with a valid x402 payment.
# First, obtain the 402 challenge:
curl -X POST https://lowpaymentfee.com/api/v1/carts/19
# Returns 402 with x402 challenge. Sign the payment for 20000 base units
# of USDC on Base, then retry with the header:
curl -X POST https://lowpaymentfee.com/api/v1/carts/19 \
-H "X-PAYMENT: <signed-payment-payload>" \
-H "Content-Type: application/json"Endpoint
Quality
The endpoint is live (returns a valid 402 challenge), but the specific resource /api/v1/carts/19 is not documented anywhere on the site. Documentation pages are empty (only showing 'Connect wallet'). No request/response schema, no examples, and no explanation of what 'Premium API Access' on a carts endpoint actually returns. Effectively a stub listing.
Warnings
- —The endpoint path /api/v1/carts/19 does not match any documented API on the landing page — its actual functionality is unknown.
- —All documentation pages (/docs, /pricing, /README, /api) returned only 'Connect wallet' with no substantive content.
- —No request body schema or response schema is available; callers cannot know what to send or what to expect back.
- —The 'Premium API Access' description is generic and does not explain the endpoint's purpose.
Citations
- —The endpoint returns a 402 challenge with maxAmountRequired of 20000 base units of USDC on Base networkhttps://lowpaymentfee.com/api/v1/carts/19
- —The platform lists APIs across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categories all at $0.02/requesthttps://lowpaymentfee.com
- —Pricing is $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —USDC asset address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/carts/19