x402 endpoint checker: decode payment terms without paying

$0.01 per call · failed calls are never charged · no account or subscription: pay per call with a card key or USDC

Check an x402 seller before you pay it: decode any public endpoint's 402 payment requirements without paying (v1 body or v2 header) into USD price for native USDC, network, asset, recipient, scheme and timeout, plus a listing-quality score for https resource URL, atomic amount, facilitator minimum, description, Bazaar metadata and output schema. Never signs. Use before buying from an unfamiliar seller or to audit your own x402 listing.

When to use it

Check an x402 seller's price, network, asset and recipient before paying it
Decode a v1 402 body or a v2 PAYMENT-REQUIRED header
Score your own x402 listing for the fields directories and the Bazaar read

Run it free (25 free calls) Buy credits by card (from $1) Example result (JSON)

Inputs

Name	Type	Description
`url` (required)	string	Absolute public https URL of the paid endpoint, with any query it needs

Request

Over HTTP, with a card key from /credits:

curl -H "Authorization: Bearer adt_…" "https://tools.funwords.eu/x402/check?url=https%3A%2F%2Fagent-data-tools.revmesh2074.workers.dev%2Fbtc-fees"

Or one of your 25 free calls, no key:

curl "https://tools.funwords.eu/x402/check?url=https%3A%2F%2Fagent-data-tools.revmesh2074.workers.dev%2Fbtc-fees&trial=1"

Without a key, the same URL answers 402 Payment Required with x402 and MPP terms, so an agent with a wallet pays per call in USDC (Base, Polygon, Arbitrum or Solana over x402; Base or Tempo over MPP) and retries.

Example result

{
  "url": "https://agent-data-tools.revmesh2074.workers.dev/btc-fees",
  "status": 402,
  "paywalled": true,
  "x402Version": 2,
  "resource": {
    "url": "https://agent-data-tools.revmesh2074.workers.dev/btc-fees",
    "description": "Current Bitcoin network fee rates… Use before sending a Bitcoin transaction…",
    "mimeType": "application/json"
  },
  "accepts": [
    {
      "scheme": "exact",
      "network": "eip155:8453",
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "payTo": "0x…",
      "amountAtomic": "2000",
      "priceUsd": 0.002,
      "assetIsNativeUsdc": true,
      "maxTimeoutSeconds": 300
    }
  ],
  "checks": [
    {
      "check": "x402 payment requirements present",
      "pass": true
    }
  ],
  "score": 1
}

From an AI agent (MCP)

Add the MCP server to Claude, Cursor or any MCP client. This tool is x402_check, and the first 25 successful calls are free:

https://tools.funwords.eu/mcp

Questions

Does it pay or sign anything?

No. It only reads the endpoint's unpaid 402 answer.

What does the listing score check?

An https resource URL, the atomic amount, the facilitator minimum, a description, Bazaar metadata and an output schema.

How do I pay?

Each successful call costs $0.01; failed calls are not charged. The first 25 calls are free. Then pay with card credits (from $1; the key goes in an Authorization header or, for clients that can only fetch a URL, as api_key= in the URL) or per call in USDC over x402 or MPP. No account is needed.