Skill: API contract drift check

Bundled execution of the API contract drift check workflow — The 'did this API contract change in a way that breaks our integration?' workflow. Diff two OpenAPI snapshots structurally, lint the new one for agent-readiness regressions, extract the endpoint surface for inventory comparison, validate a known-good payload against the new contract, and summarize security-relevant changes. Six tools, one go/no-go answer on whether the upstream API broke us. One x402 payment runs 6 underlying tools (openapi-diff, openapi-lint, openapi-extract, openapi-required-params, openapi-validate-payload, openapi-security-summary); partial-success per step.

Input

Field	Type	Description
oldSpec *	string	the prior OpenAPI snapshot as JSON or YAML
newSpec *	string	the current OpenAPI snapshot as JSON or YAML

Example output

{
  "pack": "schema-evolution",
  "args": {
    "oldSpec": "yesterday's snapshot",
    "newSpec": "today's snapshot"
  },
  "steps": [
    {
      "slug": "openapi-diff",
      "ok": true,
      "result": {}
    },
    {
      "slug": "openapi-lint",
      "ok": true,
      "result": {}
    },
    {
      "slug": "openapi-extract",
      "ok": true,
      "result": {}
    },
    {
      "slug": "openapi-required-params",
      "ok": true,
      "result": {}
    },
    {
      "slug": "openapi-validate-payload",
      "ok": true,
      "result": {}
    },
    {
      "slug": "openapi-security-summary",
      "ok": true,
      "result": {}
    }
  ],
  "summary": "6/6 steps succeeded"
}

Try it — see the 402 challenge (free)

curl -i -X POST https://agent402.tools/api/skill/schema-evolution \
  -H "Content-Type: application/json" \
  -d '{"oldSpec":"yesterday's snapshot","newSpec":"today's snapshot"}'

The response is HTTP 402 Payment Required with exact payment requirements. Any x402 v2 client pays automatically and retries:

Paid call (JavaScript agent)

import { wrapFetchWithPayment } from "@x402/fetch";
import { x402Client } from "@x402/core/client";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const client = new x402Client();
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/skill/schema-evolution", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "oldSpec": "yesterday's snapshot",
    "newSpec": "today's snapshot"
  }),
});

Wallet-only. This tool reaches the network/browser/storage, so it is paid in USDC via x402 (no proof-of-work tier).

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