# x402 Payment Failure Doctor (GET)

> x402 Payment Failure Doctor (GET) is a paid API for AI agents from gpt55.558686.xyz, paid per call via x402, $0.006/call, status down (last checked 2026-10-12).

Diagnoses why an x402 payment failed to convert from quote to settled response, identifying issues like missing payment headers, amount mismatches, wallet spend-cap blocks, verify/settle failures, or post-payment delivery problems.

## Facts

- Endpoint: POST https://gpt55.558686.xyz/v1/tools/x402-payment-failure-doctor?utm_source=zero.xyz
- Price: $0.006/call
- Payment: x402
- Status: down
- Last checked: 2026-10-12
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-payment-failure-doctor-get-cdb7e788
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_bUieApzjrxGktNE0dVyqW

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability x402-payment-failure-doctor-get-cdb7e788 -d '<json body>'
```

Example prompt: My x402 payment to https://api.example.com/data kept failing — can you diagnose what went wrong? The method was GET, I got a 402 back, the payment header was present, verify status was 200 but settle status was 500, expected payTo is 0xAbC123, network is base, and the error message was 'settle timeout'.

## When to prefer this

Use this endpoint when an x402 payment integration is not working and you need to pinpoint exactly which stage of the payment flow failed — especially when you want to inspect a live quote without actually paying the target. Prefer this over generic HTTP debuggers when the failure is specific to x402 protocol stages like verify, settle, or payment header construction. The GET variant is ideal for agents, crawlers, and wallets that cannot send JSON request bodies.

## Known failure modes

- Missing or malformed required 'input' parameter returns validation error
- URL or endpoint field exceeds 2048 character limit returns schema error
- Invalid status code values (outside 0-599) rejected
- Timeout values outside 1000-15000ms range rejected
- x402 payment of up to $0.006 USDC required; unpaid requests return 402
- Truncated or malformed paymentRequiredHeader may reduce diagnostic accuracy

## Output

Returns a structured diagnosis of the x402 payment failure, identifying which stage failed (e.g. missing header, verify, settle, or delivery), what the specific mismatch or error was, and actionable recommendations to resolve the issue. Does not send any payment to the target endpoint.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "type": "object",
     "properties": {
      "url": {
       "type": "string",
       "maxLength": 2048,
       "minLength": 1
      },
      "body": {
       "type": "object",
       "additionalProperties": true
      },
      "method": {
       "enum": [
        "GET",
        "POST",
        "PUT",
        "PATCH",
        "DELETE"
       ],
       "type": "string"
      },
      "status": {
       "type": "integer",
       "maximum": 599,
       "minimum": 0
      },
      "endpoint": {
       "type": "string",
       "maxLength": 2048,
       "minLength": 1
      },
      "resource": {
       "type": "string",
       "maxLength": 2048,
       "minLength": 1
      },
      "timeout_ms": {
       "type": "integer",
       "maximum": 15000,
       "minimum": 1000
      },
      "errorMessage": {
       "type": "string",
       "maxLength": 4000
      },
      "settleStatus": {
       "type": "integer",
       "maximum": 599,
       "minimum": 0
      },
      "verifyStatus": {
       "type": "integer",
       "maximum": 599,
       "minimum": 0
      },
      "error_message": {
       "type": "string",
       "maxLength": 4000
      },
      "expectedPayTo": {
       "type": "string",
       "maxLength": 80
      },
      "settle_status": {
       "type": "integer",
       "maximum": 599,
       "minimum": 0
      },
      "verify_status": {
       "type": "integer",
       "maximum": 599,
       "minimum": 0
      },
      "facilitatorUrl": {
       "type": "string",
       "maxLength": 2048
      },
      "expectedNetwork": {
       "type": "string",
       "maxLength": 80
      },
      "expected_pay_to": {
       "type": "string",
       "maxLength": 80
      },
      "facilitator_url": {
       "type": "string",
       "maxLength": 2048
      },
      "expected_network": {
       "type": "string",
       "maxLength": 80
      },
      "hasPaymentHeader": {
       "type": [
        "boolean",
        "string"
       ]
      },
      "has_payment_header": {
       "type": [
        "boolean",
        "string"
       ]
      },
      "quoteHeaderPresent": {
       "type": [
        "boolean",
        "string"
       ]
      },
      "expectedAmountAtomic": {
       "type": "string",
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-payment-failure-doctor-get-cdb7e788/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from gpt55.558686.xyz](https://www.zero.xyz/host/gpt55.558686.xyz/llms.txt)