x402-gated API platform on Base offering data, AI, finance, and utility endpoints at $0.02/request via USDC.
What it does
lowpaymentfee.com is an x402-protocol API marketplace that gates a collection of endpoints behind per-request USDC micropayments on the Base network. The specific endpoint at `/api/v1/inbox/159` is listed as "Premium API Access" and accepts POST requests. Payment is settled on-chain using USDC (contract 0x8335…2913 on Base) with a maximum amount of 20,000 base units, which equals $0.02 per call (USDC uses 6 decimals). No API keys, rate limits, or upfront commitments are required — callers simply attach an x402 payment header to each request.
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 listed endpoints share the same $0.02/request pricing. However, the specific endpoint being listed here (`/api/v1/inbox/159`) does not clearly map to any of these named services — its description is simply "Premium API Access" with no further documentation on what it returns or what input it expects.
The endpoint is confirmed live, returning a proper 402 challenge with x402 version 1. Documentation is extremely sparse: the /api, /pricing, and /README pages all resolve to a "Connect wallet" prompt with no additional content. There is no OpenAPI spec, no request/response schema beyond the outputSchema stub, and no examples of what the endpoint actually does.
Capabilities
Use cases
- —Paying per-request for API access without managing API keys or subscriptions
- —Integrating on-chain USDC micropayments into automated agent workflows
- —Accessing data, AI, finance, or utility endpoints via x402 protocol
Fit
Best for
- —Developers wanting zero-commitment, pay-as-you-go API access
- —AI agents that can settle x402 payments autonomously on Base
- —Projects needing low-cost per-call pricing without rate limits
Not for
- —Users who need detailed API documentation or OpenAPI specs before integrating
- —Applications requiring non-crypto payment methods
- —High-volume use cases where per-request on-chain settlement adds unacceptable latency
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/inbox/159 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-token>" \
-d '{}'Endpoint
Quality
The endpoint is live and returns a valid x402 402 challenge, confirming pricing and payment details. However, there is no documentation on what the endpoint actually does, no request/response schema, no OpenAPI spec, and the /api, /pricing, and /README pages are all empty beyond a wallet-connect prompt. The endpoint path '/api/v1/inbox/159' does not match any of the advertised service categories, making its purpose unclear.
Warnings
- —No documentation available for what /api/v1/inbox/159 actually returns or accepts as input
- —The endpoint path does not match any of the named services listed on the homepage
- —No OpenAPI spec, no request/response examples, and no README content available
- —The /api, /pricing, and /README pages all render only a 'Connect wallet' prompt with no useful information
Citations
- —The endpoint returns a 402 challenge with x402 version 1, maxAmountRequired of 20000 base units in USDC on Basehttps://lowpaymentfee.com/api/v1/inbox/159
- —All listed endpoints are priced at $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —USDC asset contract on Base is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913https://lowpaymentfee.com/api/v1/inbox/159
- —The platform advertises Data & Analytics, AI & ML, Finance & Web3, and Infrastructure endpoint categorieshttps://lowpaymentfee.com