Payments · x402 · early usage

x402 Doctor: why a payment failed, in plain words: the cause, whose side it is on (your…

by api.maxwellinternational.ai · discovered, not yet claimed by its owner · updated 2026-10-09

30d calls6

30d payers3

MethodPOST

Outputjson

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

x402 Doctor: why a payment failed, in plain words: the cause, whose side it is on (your client, your wallet, the network, the seller or the facilitator) and how to fix it, from over 40 named causes (x402 and Coinbase facilitator codes, EVM and Solana, HTTP and network errors). Send the seller 402 as challenge and the error as response, by POST JSON or GET query. Unknown failures are reviewed nightly.

Tags: developer · security · x402 · bazaar

Call contract

Method: POST
Input: json
Output: json
Last paid call: 2026-10-09

Input example from Bazaar metadata

{
  "challenge": "402",
  "response": "{\"invalidReason\":\"invalid_exact_evm_payload_signature\"}",
  "url": "https://example.com/api"
}

Output example

{
  "verdict": "client_problem"
}

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/36247.json for the price and payment options.
Pay. Call GET https://api.maxwellinternational.ai/v1/doctor/payment. 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, Solana, and an x402-capable client (see the examples below). Call the endpoint unpaid first to see exactly what it asks for.

Pricing & payment

Price: $0.005 / request
Protocol: x402 v2
Auth: No account or API key. Pay per request.
Networks: Base, Solana
Demand: 6 calls · 3 unique payers in 30d (public x402 Bazaar data)

x402 payment requirements

Scheme	Network	Asset	Amount	Pay to	Timeout
exact	Base eip155:8453	USDC	$0.005	0x5976376b0c2125655e01d0a7758c744c43fb6d93	60s
exact	Solana solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp	USDC	$0.005	u5zcwMcmrn7qAN4zUJzLhpLDQv81qtFDfZR1ohCrMs9	60s

accepts[] (raw JSON)

[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "payTo": "0x5976376b0c2125655e01d0a7758c744c43fb6d93",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "5000",
    "amountUsd": 0.005,
    "maxTimeoutSeconds": 60
  },
  {
    "scheme": "exact",
    "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
    "payTo": "u5zcwMcmrn7qAN4zUJzLhpLDQv81qtFDfZR1ohCrMs9",
    "asset": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
    "amount": "5000",
    "amountUsd": 0.005,
    "maxTimeoutSeconds": 60
  }
]

Schemas

Output schema (JSON Schema)

{
  "properties": {
    "example": {
      "type": "object"
    },
    "type": {
      "type": "string"
    }
  },
  "required": [
    "type"
  ],
  "type": "object"
}

Example shape — generated from the schema, not a captured live response

{
  "example": {},
  "type": "string"
}

Examples

curl

curl "https://api.maxwellinternational.ai/v1/doctor/payment"
# -> 402 Payment Required, accepts[] lists how to pay
# retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid

JavaScript

const res = await fetch("https://api.maxwellinternational.ai/v1/doctor/payment");
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://api.maxwellinternational.ai/v1/doctor/payment")
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: api.maxwellinternational.ai
Endpoint: https://api.maxwellinternational.ai/v1/doctor/payment
Machine-readable: /resources/36247.json