# Agent Protocol Inspector via x402 Wire v2: A Technical Tutorial

> Source: <https://contextiq.trango-compute.com/blog/agent-protocol-inspector-v2-tutorial-mcp-a2a-ard>
> Published: 2026-09-14 00:00:00+00:00

# Agent Protocol Inspector via x402 Wire v2: A Technical Tutorial

Call ContextIQ's Agent Protocol Inspector via x402 wire v2 to detect MCP, A2A, ARD, and llms.txt support on any URL, paid with @x402/fetch or an API key.

[Agent Protocol Inspector](https://contextiq.trango-compute.com/agent-readiness-detector) checks whether a URL supports MCP (Model Context Protocol), A2A (Agent2Agent), ARD (Agentic Resource Discovery), or publishes an `llms.txt` file — the signals that tell you whether a service is actually built to be used by an autonomous agent, or just a regular website an agent happens to be able to scrape. This is a tutorial for its **x402 wire v2** endpoint.

## The Endpoint

```
POST /api/v1/agent-protocol-inspector/x402-v2
Price: $0.02 per call
Body: { "url": "<URL to scan>" }
```

## The 402 Challenge

```
curl -i -X POST https://contextiq.trango-compute.com/api/v1/agent-protocol-inspector/x402-v2 \
  -H "Content-Type: application/json" \
  -d '{"url":"example.com"}'
```

Same shape as every other ContextIQ v2 route: the actual challenge is base64-encoded JSON in the `PAYMENT-REQUIRED` response header, not the body.

```
{
  "x402Version": 2,
  "resource": { "url": "https://contextiq.trango-compute.com/api/v1/agent-protocol-inspector/x402-v2" },
  "accepts": [{ "scheme": "exact", "network": "eip155:8453", "amount": "20000", "payTo": "0x4eba5ea3cf0f3fc307099317e17e54390f7a4c58", "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913" }],
  "extensions": { "bazaar": { "info": { "input": { "type": "http", "method": "POST", "schema": { "properties": { "url": { "type": "string" } }, "required": ["url"] } } } } }
}
```

## Option A: API Key

```
curl -X POST https://contextiq.trango-compute.com/api/v1/agent-protocol-inspector/x402-v2 \
  -H "Authorization: Bearer sk_live_..." \
  -H "Content-Type: application/json" \
  -d '{"url":"example.com"}'
```

## Option B: Pay With x402, No API Key

``` js
import { createWalletClient, http } from "viem";
import { privateKeyToAccount } from "viem/accounts";
import { base } from "viem/chains";
import { wrapFetchWithPayment } from "@x402/fetch";

const account = privateKeyToAccount(process.env.WALLET_PRIVATE_KEY as `0x${string}`);
const client = createWalletClient({ account, transport: http(), chain: base });
const fetchWithPayment = wrapFetchWithPayment(fetch, client);

const res = await fetchWithPayment("https://contextiq.trango-compute.com/api/v1/agent-protocol-inspector/x402-v2", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({ url: "example.com" }),
});

console.log(await res.json());
```

## The Response

Real output from a live scan (ContextIQ's own domain, run today):

```
{
  "target": "https://contextiq.trango-compute.com",
  "origin": "https://contextiq.trango-compute.com",
  "protocols": {
    "mcp": { "status": "not_detected", "evidence": [] },
    "a2a": { "status": "not_detected", "evidence": [] },
    "ard": { "status": "not_detected", "evidence": [] }
  },
  "llmsTxt": { "found": true, "url": "https://contextiq.trango-compute.com/llms.txt" },
  "detectedCount": 0
}
```

Each protocol's `status` is `confirmed` (found and validated), `indicated` (some signal, e.g. a route exists but didn't fully validate), or `not_detected`. `evidence` names exactly what was checked and found, so a `confirmed` result isn't a black-box claim — you can see the specific `.well-known` path or response header that triggered it. `detectedCount` is a quick sum across the three protocols; `llmsTxt` is tracked separately since it's a content convention, not an agent-callable protocol.

Worth internalizing from real-world scanning: most of the internet, including plenty of services that are perfectly usable by an agent via plain HTTP, will show `detectedCount: 0`. That's expected, not a failure — this tool answers "does this URL declare agent-native protocol support," not "can an agent use this at all."

## Try It

[Agent Protocol Inspector](https://contextiq.trango-compute.com/agent-readiness-detector) is free from the dashboard, or callable via the API above for checking a counterparty's agent-readiness before your own agent decides how to integrate with it.

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