Blockchain Data · x402

Two checks in one

by modell.halowerk.com · discovered, not yet claimed by its owner · updated 2026-10-11

Mirrored from Coinbase's public x402 Bazaar. The description is the provider's own text and has not been reviewed here; the payment requirements are copied as published.

What it does

Two checks in one. First the arguments are validated against the tool input schema and every violation is reported with its path and a sentence saying what to change. Second, values that satisfy the schema but look wrong are flagged: an unset required field filled with a placeholder like "string" or "TODO", a number at a suspicious order of magnitude, an address that fails its checksum shape, a destructive flag set to true, an empty string where content was expected.

Tags: bazaar

Use with an agent

Discover. Agents find this listing with GET https://bazaar.saylorinnovations.com/discovery/search?query=…, the MCP tool search_resources, or /discovery/resources.
Inspect. Fetch /resources/40914.json for the price and payment options.
Pay. Call GET https://modell.halowerk.com/v1/tool-arg-validate. The provider answers 402 with its payment requirements. An x402 client signs one of the options below and retries with PAYMENT-SIGNATURE.
Execute. The provider returns 200 with the data. Agent Bazaar is not in the request path and never sees your payment.

For humans

You don't need an account or an API key; you need a wallet holding a small amount of USDC on Base, and an x402-capable client (see the examples below). Call the endpoint unpaid first to see exactly what it asks for.

Pricing & payment

Price: $0.002 / request
Protocol: x402 v2
Auth: No account or API key. Pay per request.
Networks: Base
Calls (30d): 2 · 2 unique payers (third-party data from the public x402 Bazaar)

x402 payment requirements

Scheme	Network	Asset	Amount	Pay to	Timeout
exact	Base eip155:8453	USDC	$0.002	0x2880EdfFF13100677Bf97A3CBdF3Bc34771C4E5E	300s

accepts[] (raw JSON)

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0x2880EdfFF13100677Bf97A3CBdF3Bc34771C4E5E",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "2000",
    "amountUsd": 0.002,
    "maxTimeoutSeconds": 300
  }
]

Examples

curl

curl "https://modell.halowerk.com/v1/tool-arg-validate"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

JavaScript

const res = await fetch("https://modell.halowerk.com/v1/tool-arg-validate");
if (res.status === 402) {
  const { accepts } = await res.json();
  // pay one of accepts[] via an x402 client, then retry with the payment header
}

Python

import httpx
res = httpx.get("https://modell.halowerk.com/v1/tool-arg-validate")
if res.status_code == 402:
    accepts = res.json()["accepts"]
    # pay one of accepts[] via an x402 client, then retry with the payment header

Details

Provider: modell.halowerk.com
Endpoint: https://modell.halowerk.com/v1/tool-arg-validate
Machine-readable: /resources/40914.json