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 USDC micropayments on the Base network. The specific endpoint `/api/v1/carts/37` is listed as "Premium API Access" and requires a payment of up to 20,000 base units of USDC (0.02 USD) per call via the x402 exact payment scheme. No API keys or rate limits are required — callers simply attach an X-PAYMENT header with a valid payment proof.
The broader platform advertises four categories of endpoints: 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 the same $0.02 per request price point and settle payments to address 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3 using USDC (contract 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Base.
Documentation is extremely sparse — the /docs, /pricing, /api, and /README pages all render only a "Connect wallet" prompt with no further content. There is no OpenAPI spec, no request/response schema documentation, and no example payloads available. The endpoint is confirmed live (returns 402 with a valid x402 challenge), but without documentation it is unclear what request body the POST expects or what response payload it returns.
Capabilities
Use cases
- —Programmatic access to data, AI, finance, or utility APIs without managing API keys or subscriptions
- —Agent-driven workflows that need on-demand API calls settled via crypto micropayments
- —Testing x402 protocol integrations with a low-cost endpoint
Fit
Best for
- —Developers exploring x402 pay-per-call patterns on Base
- —AI agents that can autonomously pay for API access with USDC
- —Users who want no-commitment, no-signup API access
Not for
- —Production workloads requiring documented request/response schemas and SLAs
- —Users without access to USDC on the Base network
- —High-volume use cases where $0.02/request adds up significantly
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/carts/37 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>"Endpoint
Quality
The endpoint is confirmed live with a valid x402 402 challenge, but documentation is essentially nonexistent — all doc pages show only 'Connect wallet'. There is no OpenAPI spec, no request/response schema, and no examples. The specific purpose of /api/v1/carts/37 is unclear beyond the generic 'Premium API Access' label. Pricing is clear but everything else must be inferred.
Warnings
- —No documentation available — /docs, /pricing, /api, and /README all render only a 'Connect wallet' prompt
- —No OpenAPI or schema definition for any endpoint
- —The specific function of /api/v1/carts/37 ('Premium API Access') is not explained anywhere
- —No request body schema or response format documented — callers must experiment
- —The broader platform lists many endpoints but none have documented schemas
Citations
- —The endpoint returns a 402 x402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/carts/37
- —All endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant accesshttps://lowpaymentfee.com
- —The platform offers endpoints in Data & Analytics, AI & Machine Learning, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com
- —USDC asset contract is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base networkhttps://lowpaymentfee.com/api/v1/carts/37
- —Documentation pages (/docs, /pricing, /api, /README) render only 'Connect wallet'https://lowpaymentfee.com/docs