Pay-per-call API platform on Base with USDC payments via x402 — $0.02/request, no API keys required.
What it does
lowpaymentfee.com is a pay-per-request API platform that uses the x402 protocol to accept USDC payments on the Base network. The specific endpoint `/api/v1/invoices/13` is listed as "Premium API Access" and returns JSON. The x402 challenge indicates a max cost of 20,000 base units of USDC (0.02 USD per call), consistent with the site's advertised $0.02/request pricing across all endpoints.
The broader platform advertises multiple API categories including 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 uniformly at $0.02 per request with no API keys, no rate limits, and no minimum commitments.
However, the specific functionality of the `/api/v1/invoices/13` endpoint is unclear — it does not appear in the site's listed API catalog, and the description "Premium API Access" is generic. Documentation pages (`/docs`, `/pricing`, `/README`) returned only a "Connect wallet" prompt with no substantive content. There is no OpenAPI schema, no request/response examples, and no detailed documentation available for any endpoint.
Capabilities
Use cases
- —Accessing premium API data with per-request USDC micropayments on Base
- —Agent-driven API consumption without pre-registration or API keys
- —Programmatic invoice retrieval or generation
Fit
Best for
- —Developers wanting zero-signup, pay-as-you-go API access
- —AI agents that can settle x402 payments autonomously
- —Users who prefer crypto micropayments over subscription billing
Not for
- —Users needing detailed API documentation or OpenAPI specs before integrating
- —High-volume consumers who need bulk pricing or rate-limit guarantees
- —Anyone without a Base-compatible USDC wallet
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/invoices/13
# Returns 402 with x402 payment challenge.
# Include X-PAYMENT header with a valid x402 payment proof to access the resource.Endpoint
Quality
The endpoint is live (402 challenge confirmed) and pricing is clear ($0.02 USDC on Base), but there is no documentation, no OpenAPI schema, no request/response examples, and the specific purpose of /api/v1/invoices/13 is undocumented. All doc pages returned only 'Connect wallet' with no content.
Warnings
- —The endpoint /api/v1/invoices/13 does not appear in the site's listed API catalog — its specific functionality is unknown.
- —No documentation is available: /docs, /pricing, /README, and /api all return only a 'Connect wallet' prompt with no substantive content.
- —No OpenAPI schema or request/response examples are provided for any endpoint.
- —The platform lists many API categories (AI, analytics, finance, infrastructure) but none can be verified for actual functionality from the crawl data.
Citations
- —The x402 challenge returns maxAmountRequired of 20000 base units of USDC on Base networkhttps://lowpaymentfee.com/api/v1/invoices/13
- —All 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 advertises Data & Analytics, AI & ML, Finance & Web3, and Infrastructure API categorieshttps://lowpaymentfee.com
- —USDC asset address 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/invoices/13