Pay-per-request API platform on Base network via x402 — $0.02/call in USDC.
What it does
lowpaymentfee.com is an x402-enabled API platform that offers a broad catalog of pay-per-request endpoints across data analytics, AI/ML inference, finance/Web3, and infrastructure utilities. All endpoints are settled on the Base network using USDC, with a uniform price of $0.02 per request. The platform requires no API keys, no rate limits, and no upfront commitments — callers simply attach an x402 payment header to each request.
The specific endpoint at `/api/v1/inbox/153` is listed as "Premium API Access" and returns a 402 challenge requesting up to 20,000 base units of USDC (0.02 USD, since USDC uses 6 decimals) on Base. The payment is made to address `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3` using the exact payment scheme. The endpoint accepts POST requests and returns `application/json`.
The broader platform advertises endpoints for sentiment analysis, text summarization, classification, embeddings, price feeds, exchange rates, token quotes, gas estimates, geocoding, validation, conversion, and generation. However, no OpenAPI schema, detailed documentation, or example request/response payloads were found during the crawl — the /api, /pricing, and /README pages all returned only a "Connect wallet" prompt with no substantive content. The actual behavior and input/output contracts of this specific inbox endpoint (and the other listed endpoints) remain undocumented.
Capabilities
Use cases
- —Agents that need on-demand API access without pre-registration or API keys
- —Programmatic access to utility endpoints with per-call crypto micropayments
- —Testing x402 payment flows on the Base network
Fit
Best for
- —Developers or agents wanting zero-signup, pay-as-you-go API access
- —x402-compatible agents settling in USDC on Base
- —Low-volume or sporadic API consumers who prefer no subscriptions
Not for
- —Users needing detailed API documentation or guaranteed SLAs
- —High-volume consumers who would benefit from bulk pricing or rate-limit guarantees
- —Users who cannot transact in USDC on the Base network
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/inbox/153 \
-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 with clear pricing. However, there is no OpenAPI schema, no documentation, no example requests or responses, and the specific purpose of the '/api/v1/inbox/153' endpoint is entirely unclear beyond the generic label 'Premium API Access'. The crawled docs pages were empty (wallet-connect prompts only).
Warnings
- —No OpenAPI or schema documentation available for any endpoint
- —The specific function of /api/v1/inbox/153 is undocumented — 'Premium API Access' is a generic label
- —All non-root pages (/api, /pricing, /README) returned no useful content
- —Input and output contracts are unknown; callers cannot determine what to send or expect back
Citations
- —Endpoint returns a 402 x402 challenge requesting 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/inbox/153
- —Platform advertises $0.02 per request with no API keys, no rate limits, and instant access on Base networkhttps://lowpaymentfee.com
- —USDC asset address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Basehttps://lowpaymentfee.com/api/v1/inbox/153