Pay-per-call API platform on Base (USDC) covering data, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402-enabled API platform that offers a broad suite of endpoints spanning data & analytics, AI & machine learning, finance & Web3, and infrastructure utilities. All endpoints are paid per-request using USDC on the Base network via the x402 protocol — no API keys, no rate limits, and no subscriptions required.
The specific endpoint at `/api/v1/inbox/3` is listed as "Premium API Access" and accepts POST requests. Its x402 challenge advertises a maximum cost of 20,000 base units of USDC (0x8335…2913 on Base), which equals $0.02 per call (USDC uses 6 decimals). The platform's landing page confirms a uniform $0.02/request pricing across all listed endpoints. Other endpoints on the platform include sentiment analysis, text summarization, classification, embeddings, price feeds, exchange rates, geocoding, validation, and more.
Documentation is minimal — the /api, /pricing, and /README pages all resolve to a "Connect wallet" prompt with no further content. There is no OpenAPI spec, no request/response schema documentation, and no usage examples beyond the endpoint listing on the homepage. The endpoint is confirmed live (HTTP 402 challenge returned on POST), but without documentation it is unclear what request body `/api/v1/inbox/3` expects or what it returns.
Capabilities
Use cases
- —Accessing premium API functionality with per-call USDC micropayments on Base
- —Agent-driven workflows that need keyless, pay-as-you-go API access
- —Integrating low-cost data, AI, or utility endpoints without subscription commitments
Fit
Best for
- —Developers who want zero-setup, pay-per-use API access via crypto
- —AI agents that can settle x402 payments autonomously on Base
- —Projects needing cheap per-call pricing without API key management
Not for
- —Users who need detailed API documentation or OpenAPI specs before integrating
- —Applications requiring non-crypto payment methods
- —High-volume use cases where subscription pricing would be more economical
Quick start
# The endpoint requires an x402 payment header (USDC on Base).
# Using curl to see the 402 challenge:
curl -X POST https://lowpaymentfee.com/api/v1/inbox/3 \
-H 'Content-Type: application/json'
# Returns 402 with x402 payment challenge.
# Supply X-PAYMENT header with valid payment proof to access.Endpoint
Quality
The endpoint is confirmed live via a valid x402 402 challenge, and pricing is clear ($0.02/request in USDC on Base). However, there is no OpenAPI spec, no request/response schema, no documentation beyond the homepage listing, and the specific purpose of /api/v1/inbox/3 is undocumented. This is effectively a stub listing.
Warnings
- —No API documentation available — /api, /pricing, and /README pages only show 'Connect wallet'
- —No OpenAPI or schema definition found for any endpoint
- —The purpose and expected input/output of /api/v1/inbox/3 ('Premium API Access') is completely undocumented
- —Cannot verify what data or service this specific endpoint provides
Citations
- —Uniform pricing of $0.02 per request across all endpointshttps://lowpaymentfee.com
- —No API keys, no rate limits, instant access, Base networkhttps://lowpaymentfee.com
- —x402 challenge returns maxAmountRequired of 20000 base units of USDC (0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913) on Basehttps://lowpaymentfee.com/api/v1/inbox/3
- —Platform offers endpoints in data & analytics, AI & ML, finance & Web3, and infrastructure categorieshttps://lowpaymentfee.com