A2A Agent Card validate

Validate an A2A (Agent2Agent protocol) Agent Card: required fields, skill shape, transport names, capability flags — spec v0.3 structural core. Returns errors, interop warnings, and a normalized summary (skills, interfaces, capabilities). Deterministic mini-A2A tooling — check a card before your agent trusts it.

Input

Field	Type	Description
card *	object	the Agent Card JSON (object or JSON string)

Example output

{
  "valid": true,
  "errors": [],
  "warnings": [],
  "summary": {
    "name": "Sample Weather Agent",
    "skillCount": 1
  }
}

Try it — see the 402 challenge (free)

curl -i -X POST https://agent402.tools/api/a2a-card-validate \
  -H "Content-Type: application/json" \
  -d '{"card":{"protocolVersion":"0.3.0","name":"Sample Weather Agent","description":"A sample A2A Agent Card served as a static example for card tooling. This describes a fictional weather agent, not a live A2A endpoint.","url":"https://example.com/a2a/v1","preferredTransport":"JSONRPC","version":"1.0.0","provider":{"organization":"Example Org","url":"https://example.com"},"capabilities":{"streaming":true,"pushNotifications":false,"stateTransitionHistory":false},"defaultInputModes":["application/json","text/plain"],"defaultOutputModes":["application/json"],"skills":[{"id":"get-forecast","name":"Get weather forecast","description":"Returns a city's 5-day forecast.","tags":["weather","forecast"],"examples":["What is the weather in Paris this week?"]}]}}'

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/a2a-card-validate", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "card": {
      "protocolVersion": "0.3.0",
      "name": "Sample Weather Agent",
      "description": "A sample A2A Agent Card served as a static example for card tooling. This describes a fictional weather agent, not a live A2A endpoint.",
      "url": "https://example.com/a2a/v1",
      "preferredTransport": "JSONRPC",
      "version": "1.0.0",
      "provider": {
        "organization": "Example Org",
        "url": "https://example.com"
      },
      "capabilities": {
        "streaming": true,
        "pushNotifications": false,
        "stateTransitionHistory": false
      },
      "defaultInputModes": [
        "application/json",
        "text/plain"
      ],
      "defaultOutputModes": [
        "application/json"
      ],
      "skills": [
        {
          "id": "get-forecast",
          "name": "Get weather forecast",
          "description": "Returns a city's 5-day forecast.",
          "tags": [
            "weather",
            "forecast"
          ],
          "examples": [
            "What is the weather in Paris this week?"
          ]
        }
      ]
    }
  }),
});

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=a2a-card-validate")).json();
let n = 0;
while (lz(createHash("sha256").update(c.challenge + ":" + n).digest()) < c.difficulty) n++;
await fetch("https://agent402.tools/api/a2a-card-validate", { method: "POST", headers: { "X-Pow-Solution": c.token + ":" + n, "Content-Type": "application/json" }, body: JSON.stringify({"card":{"protocolVersion":"0.3.0","name":"Sample Weather Agent","description":"A sample A2A Agent Card served as a static example for card tooling. This describes a fictional weather agent, not a live A2A endpoint.","url":"https://example.com/a2a/v1","preferredTransport":"JSONRPC","version":"1.0.0","provider":{"organization":"Example Org","url":"https://example.com"},"capabilities":{"streaming":true,"pushNotifications":false,"stateTransitionHistory":false},"defaultInputModes":["application/json","text/plain"],"defaultOutputModes":["application/json"],"skills":[{"id":"get-forecast","name":"Get weather forecast","description":"Returns a city's 5-day forecast.","tags":["weather","forecast"],"examples":["What is the weather in Paris this week?"]}]}}) });

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