x402-gated API suite on Base: analytics, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402-protocol API marketplace offering a broad set of 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 utilities (geocoding, validation, conversion, generation). All endpoints are priced at $0.02 per request, paid in USDC on the Base network with no API keys, rate limits, or commitments required.
The specific endpoint listed here — `/api/v1/carts/35` — is labeled "Premium API Access" and returns a live x402 challenge requesting up to 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 by including an X-PAYMENT header with a signed payment proof. The endpoint accepts POST requests and returns application/json.
Documentation beyond the landing page is sparse — the /docs, /pricing, /api, and /README pages all render only a "Connect wallet" prompt with no additional technical detail. There is no OpenAPI spec, no request/response schema documentation, and no example payloads available. The purpose of the `/api/v1/carts/35` resource specifically is unclear; it does not map to any of the advertised API categories on the homepage, so its actual functionality is unknown.
Capabilities
Use cases
- —Accessing AI inference endpoints (sentiment, summarization, classification, embeddings) without API key signup
- —Fetching real-time financial data like token quotes, gas estimates, and exchange rates on a per-request basis
- —Running analytics queries or data exports with instant crypto-settled micropayments
- —Using utility services like geocoding or data validation without rate limits
Fit
Best for
- —Developers wanting zero-signup, pay-per-use API access
- —AI agents that can settle x402 payments autonomously on Base
- —Projects needing low-cost micropayment-gated endpoints
Not for
- —Users who need detailed API documentation or OpenAPI specs before integrating
- —Applications requiring high-volume bulk pricing or subscription plans
- —Users without access to USDC on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/carts/35 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <signed-x402-payment-proof>"Endpoint
Quality
The endpoint is live and returns a valid x402 challenge, but there is no documentation, no OpenAPI spec, no request/response schema, and the specific /api/v1/carts/35 resource doesn't correspond to any advertised API category. All doc pages beyond the landing page are empty wallet-connect stubs.
Warnings
- —The endpoint path /api/v1/carts/35 does not match any of the advertised API categories on the homepage; its actual functionality is unknown.
- —No OpenAPI spec, request schema, or response schema is available.
- —All documentation pages (/docs, /pricing, /api, /README) render only a 'Connect wallet' prompt with no technical content.
- —The provider site lists many endpoints but none have documented input/output schemas.
Citations
- —All endpoints priced at $0.02 per request with no API keys, rate limits, or commitmentshttps://lowpaymentfee.com
- —Endpoints span Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com
- —Payment in USDC on Base networkhttps://lowpaymentfee.com
- —x402 challenge returns maxAmountRequired of 20000 base units of USDC (asset 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) which equals $0.02https://lowpaymentfee.com/api/v1/carts/35