OpenAPI to curl command

Build a runnable curl command for one operation in an OpenAPI 3.x or Swagger 2.x spec. Locate the operation by operationId (preferred) or by method + path, substitute path parameters using the spec's example values, include required query and header parameters with their example values, and attach a JSON body when the operation defines one. Returns the structured request (method, url, headers, body) alongside the assembled curl string with POSIX single-quote escaping. Pure CPU — deterministic, no network, no $ref dereferencing.

Input

Field	Type	Description
spec *	any	OpenAPI/Swagger document (object or JSON string)
operationId	any	operationId of the operation to render (preferred)
method	any	HTTP method (use with `path` if no operationId)
path	any	Path template (use with `method` if no operationId)

Example output

{
  "method": "GET",
  "url": "https://api.example.com/users/u_42?fields=name%2Cemail",
  "headers": {},
  "body": null,
  "curl": "curl -X GET 'https://api.example.com/users/u_42?fields=name%2Cemail'"
}

Try it — see the 402 challenge (free)

curl -i -X POST https://agent402.tools/api/openapi-to-curl \
  -H "Content-Type: application/json" \
  -d '{"spec":{"openapi":"3.0.0","servers":[{"url":"https://api.example.com"}],"paths":{"/users/{id}":{"get":{"operationId":"getUser","parameters":[{"name":"id","in":"path","required":true,"schema":{"type":"string","example":"u_42"}},{"name":"fields","in":"query","required":true,"schema":{"type":"string","example":"name,email"}}],"responses":{"200":{"description":"ok"}}}}}},"operationId":"getUser"}'

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-to-curl", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "spec": {
      "openapi": "3.0.0",
      "servers": [
        {
          "url": "https://api.example.com"
        }
      ],
      "paths": {
        "/users/{id}": {
          "get": {
            "operationId": "getUser",
            "parameters": [
              {
                "name": "id",
                "in": "path",
                "required": true,
                "schema": {
                  "type": "string",
                  "example": "u_42"
                }
              },
              {
                "name": "fields",
                "in": "query",
                "required": true,
                "schema": {
                  "type": "string",
                  "example": "name,email"
                }
              }
            ],
            "responses": {
              "200": {
                "description": "ok"
              }
            }
          }
        }
      }
    },
    "operationId": "getUser"
  }),
});

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-to-curl")).json();
let n = 0;
while (lz(createHash("sha256").update(c.challenge + ":" + n).digest()) < c.difficulty) n++;
await fetch("https://agent402.tools/api/openapi-to-curl", { method: "POST", headers: { "X-Pow-Solution": c.token + ":" + n, "Content-Type": "application/json" }, body: JSON.stringify({"spec":{"openapi":"3.0.0","servers":[{"url":"https://api.example.com"}],"paths":{"/users/{id}":{"get":{"operationId":"getUser","parameters":[{"name":"id","in":"path","required":true,"schema":{"type":"string","example":"u_42"}},{"name":"fields","in":"query","required":true,"schema":{"type":"string","example":"name,email"}}],"responses":{"200":{"description":"ok"}}}}}},"operationId":"getUser"}) });

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