x402-gated API platform on Base offering data, AI, finance, and utility endpoints at $0.02/request.
What it does
lowpaymentfee.com is an x402-protocol API marketplace that gates a variety of endpoints behind per-request micropayments settled in USDC on the Base network. The specific endpoint at `/api/v1/inbox/136` is listed as "Premium API Access" and accepts POST requests with an x402 payment of up to $0.02 per call (20,000 base units of USDC with 6 decimals). No API keys or rate limits are required — callers simply attach an X-PAYMENT header with a valid x402 payment proof.
The broader platform advertises four categories of APIs: 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. The `/api/v1/inbox/136` endpoint does not have detailed documentation specifying its exact functionality beyond the generic "Premium API Access" label, so its precise behavior is unclear.
Payments are made to address `0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3` using USDC (`0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`) on Base. The x402 challenge was successfully captured with version 1 of the protocol, confirming the endpoint is live. However, no OpenAPI schema, detailed request/response documentation, or usage examples were found in the crawl.
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 x402-compatible endpoints into automated pipelines without subscription overhead
Fit
Best for
- —Developers wanting zero-commitment, pay-per-use API access
- —AI agents that can settle x402 payments autonomously on Base
- —Projects needing keyless API access with no rate limits
Not for
- —Users who need detailed API documentation and guaranteed SLAs before integrating
- —Applications requiring non-crypto payment methods (no fiat option available)
- —Use cases needing high-volume bulk pricing or subscription discounts
Quick start
curl -X POST https://lowpaymentfee.com/api/v1/inbox/136 \
-H "Content-Type: application/json" \
-H "X-PAYMENT: <x402-payment-proof>" \
-d '{}'Endpoint
Quality
The endpoint is confirmed live via a valid x402 402 challenge, and pricing is clear ($0.02 USDC on Base). However, the specific endpoint '/api/v1/inbox/136' has no documentation beyond the label 'Premium API Access' — no request schema, no response schema, no examples, and no explanation of what it actually does. The crawl pages beyond the homepage returned only 'Connect wallet' with no useful content.
Warnings
- —The exact functionality of /api/v1/inbox/136 is undocumented — 'Premium API Access' is the only description available.
- —No OpenAPI spec, request schema, or response schema was found for this or any endpoint on the platform.
- —The /api, /pricing, and /README pages returned no meaningful content in the crawl (only 'Connect wallet').
- —This endpoint may be a generic inbox/catch-all rather than a specific service — purpose is unclear.
Citations
- —The endpoint returns a valid x402 challenge with maxAmountRequired of 20000 base units of USDC on Basehttps://lowpaymentfee.com/api/v1/inbox/136
- —All 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 address is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 and payTo is 0x1A2B13E97f5F837C8F9FA1F95a1484B7C70d85F3https://lowpaymentfee.com/api/v1/inbox/136
- —Platform offers Data & Analytics, AI & ML, Finance & Web3, and Infrastructure API categorieshttps://lowpaymentfee.com