Pay-per-call API platform on Base (USDC) offering data, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402-enabled API platform that provides a broad catalog of pay-per-request endpoints settled in USDC on the Base network. The specific endpoint `/api/v1/inbox/128` 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 protocol — no API keys, accounts, or subscriptions are required; callers attach an X-PAYMENT header with a signed USDC payment to each request.
The broader platform advertises four endpoint 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 listed endpoints share the same $0.02/request pricing. The platform claims no rate limits and no minimum commitments.
Important caveat: the specific functionality behind `/api/v1/inbox/128` is not documented beyond the label "Premium API Access." There is no OpenAPI schema, no request/response examples, and no detailed documentation available from the crawled pages. The endpoint is confirmed live (returns a valid 402 challenge), but what it actually does when paid is unknown from the available material.
Capabilities
Use cases
- —Programmatic access to paid API endpoints without account registration
- —Agent-driven workflows that need instant, keyless API access settled in USDC
- —Testing x402 payment flows on Base network
Fit
Best for
- —Developers or agents wanting frictionless pay-per-call API access
- —x402-compatible wallets and agent frameworks on Base
- —Use cases where avoiding API key management is valuable
Not for
- —Users who need detailed documentation or guaranteed SLAs before purchasing
- —Anyone without a Base-network USDC wallet or x402-compatible client
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/inbox/128 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <signed-x402-payment-header>"Endpoint
Quality
The endpoint is live and returns a valid x402 402 challenge, but there is zero documentation on what /api/v1/inbox/128 actually does, no request/response schema, and no examples. The crawled pages beyond the homepage returned only 'Connect wallet' with no useful content. This is effectively a stub listing.
Warnings
- —No documentation exists for the specific endpoint /api/v1/inbox/128 — its actual functionality is unknown
- —No OpenAPI schema, request format, or response format is available
- —The /api, /pricing, and /README pages returned no useful content (just 'Connect wallet')
- —The 'inbox' path segment is unusual and may indicate a mailbox or messaging function, but this is unconfirmed
Citations
- —The endpoint returns a valid x402 challenge with maxAmountRequired of 20000 base units of USDC on Base networkhttps://lowpaymentfee.com/api/v1/inbox/128
- —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
- —The platform offers endpoints across Data & Analytics, AI & ML, Finance & Web3, and Infrastructure categorieshttps://lowpaymentfee.com
- —USDC asset address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/inbox/128