Changelog Openapi API — Pay Per Call with USDC on Base

changelog_openapi API

Diff two OpenAPI specs and generate a structured breaking-change changelog. Deterministic, no LLM. Provide base_spec_url and new_spec. Part of the x402 Gateway — $0.005 per call, settled in USDC on Base. No accounts, no API keys: agents pay per request via the x402 protocol.

How payment works

Send a POST to https://x402.freeq.one/tools/changelog_openapi without a payment header and the API replies 402 Payment Required with an x402 challenge (payTo address, USDC amount, Base network). A paying agent signs the USDC payment and retries with the PAYMENT-SIGNATURE header (base64 JSON payment payload) — settlement is verified on-chain in seconds and the API response returns with a PAYMENT-RESPONSE receipt header.

Example call

curl -X POST https://x402.freeq.one/tools/changelog_openapi \
  -H "Content-Type: application/json" \
  -d '{"base_spec_url": "https://example.com/openapi-v1.json", "new_spec": {"openapi": "3.1.0", "info": {"title": "v2"}, "paths": {}}}'

Browse every pay-per-call API on the all APIs page, or inspect the machine-readable service card and OpenAPI spec.