OpenAPI / Swagger diff

Compare two OpenAPI 3.x or Swagger 2.x documents and return a structured diff: added / removed / changed endpoints, with a conservative "is any change breaking?" flag. Breaking = an endpoint or required-2xx status was removed, a required parameter was added, an optional param became required, a param type changed, or a JSON body field became required. Pure CPU — deterministic, no network, no $ref dereferencing (resolve refs upstream if needed).

Input

Field	Type	Description
before *	any	OpenAPI/Swagger document (object or JSON string) for the previous version
after *	any	OpenAPI/Swagger document (object or JSON string) for the new version

Example output

{
  "added": [
    "POST /admin"
  ],
  "removed": [
    "GET /legacy"
  ],
  "changed": [],
  "breaking": true,
  "breakingCount": 1,
  "summary": {
    "added": 1,
    "removed": 1,
    "changed": 0
  }
}

Try it — see the 402 challenge (free)

curl -i -X POST https://agent402.tools/api/openapi-diff \
  -H "Content-Type: application/json" \
  -d '{"before":{"openapi":"3.0.0","paths":{"/users":{"get":{"responses":{"200":{}}}},"/legacy":{"get":{"responses":{"200":{}}}}}},"after":{"openapi":"3.0.0","paths":{"/users":{"get":{"responses":{"200":{}}}},"/admin":{"post":{"responses":{"201":{}}}}}}}'

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/openapi-diff", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "before": {
      "openapi": "3.0.0",
      "paths": {
        "/users": {
          "get": {
            "responses": {
              "200": {}
            }
          }
        },
        "/legacy": {
          "get": {
            "responses": {
              "200": {}
            }
          }
        }
      }
    },
    "after": {
      "openapi": "3.0.0",
      "paths": {
        "/users": {
          "get": {
            "responses": {
              "200": {}
            }
          }
        },
        "/admin": {
          "post": {
            "responses": {
              "201": {}
            }
          }
        }
      }
    }
  }),
});

No wallet? Pay with compute

This is a pure-CPU tool, so an agent without a wallet can pay with proof-of-work instead of USDC: fetch a challenge, solve the sha256 puzzle (16 leading zero bits — a fraction of a second of CPU, no money, no AI tokens), and resend with the X-Pow-Solution header.

import { createHash } from "node:crypto";
const lz = (b) => { let t = 0; for (const x of b) { if (!x) { t += 8; continue; } t += Math.clz32(x) - 24; break; } return t; };
const c = await (await fetch("https://agent402.tools/api/pow/challenge?slug=openapi-diff")).json();
let n = 0;
while (lz(createHash("sha256").update(c.challenge + ":" + n).digest()) < c.difficulty) n++;
await fetch("https://agent402.tools/api/openapi-diff", { method: "POST", headers: { "X-Pow-Solution": c.token + ":" + n, "Content-Type": "application/json" }, body: JSON.stringify({"before":{"openapi":"3.0.0","paths":{"/users":{"get":{"responses":{"200":{}}}},"/legacy":{"get":{"responses":{"200":{}}}}}},"after":{"openapi":"3.0.0","paths":{"/users":{"get":{"responses":{"200":{}}}},"/admin":{"post":{"responses":{"201":{}}}}}}}) });

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