# Facilitator Preemption Attack Exposure Audit for Agent Payment Rails

> Facilitator Preemption Attack Exposure Audit for Agent Payment Rails is a paid API for AI agents from k2so.wrong.systems, paid per call via x402, $0.002/call, status down (last checked 2026-10-31).

Audits whether an x402 payment facilitator can front-run, preempt, reorder, or suppress an agent's transactions, returning an exposure verdict and mitigations per attack class.

## Facts

- Endpoint: GET https://k2so.wrong.systems/api/services/facilitator-preemption-attack-exposure-audit-for?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: down
- Last checked: 2026-10-31
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/facilitator-preemption-attack-exposure-audit-for-agent-payment-rails-c9647623
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_NJbuwkQI1lx6te7pXYim8

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 facilitator-preemption-attack-exposure-audit-for-agent-payment-rails-c9647623
```

Example prompt: Run a preemption attack exposure audit on my x402 facilitator — check whether it can front-run, reorder, or suppress my agent's transactions given its current settlement path and mempool visibility, and tell me whether I should keep paying through it or switch.

## When to prefer this

Choose this endpoint when an AI agent needs to evaluate a specific x402 payment facilitator's trustworthiness before routing funds, especially when operating unattended and unable to manually verify transaction ordering integrity. Prefer this over generic blockchain security audits when the concern is specifically facilitator-level MEV-style attacks on x402 rails.

## Known failure modes

- Insufficient input about facilitator identity or settlement path may yield an inconclusive verdict
- Mempool visibility data not provided may result in incomplete front-run exposure assessment
- If the facilitator is unknown or unlisted, the evidence checklist may be sparse
- LLM-generated procedures may reflect training cutoff rather than latest protocol changes
- Network or payment failure returns no verdict

## How this service works

Audit procedure for whether an agent's payment facilitator can front-run, preempt, or reorder agent transactions on x402 rails. Inputs: facilitator identity, settlement path, mempool visibility, transaction submission order, and any relay/replace capabilities. Output: exposure verdict per attack class (front-run, preempt, reorder, suppress), evidence checklist for each, a pay/no-pay rule for that facilitator, and mitigations (private submission, direct-to-settler path, receipt cross-check). For

## Output

Returns a JSON object containing an exposure verdict for each attack class (front-run, preempt, reorder, suppress), an evidence checklist for each class, a pay/no-pay rule for the facilitator, and concrete mitigations such as private submission channels, direct-to-settler routing, and receipt cross-checking. The response includes a prose decision procedure (120+ words) and metadata including generation source and timestamp.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "meta": {
       "enum": [
        "0",
        "1"
       ],
       "type": "string",
       "description": "Set to 1 for free metadata JSON (no payment required)"
      },
      "topic": {
       "type": "string",
       "description": "Optional topic override for the decision procedure"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "title": "Facilitator Preemption Attack Exposure Audit for Agent Payment Rails paid response",
     "$schema": "https://json-schema.org/draft/2020-12/schema",
     "required": [
      "ok",
      "paid",
      "service",
      "provider",
      "result"
     ],
     "properties": {
      "ok": {
       "type": "boolean"
      },
      "paid": {
       "type": "boolean"
      },
      "result": {
       "type": "object",
       "required": [
        "ok",
        "service"
       ],
       "properties": {
        "ok": {
         "type": "boolean",
         "description": "Handler success"
        },
        "brief": {
         "type": "string",
         "description": "Decision procedure prose for agents"
        },
        "model": {
         "type": "string"
        },
        "topic": {
         "type": "string"
        },
        "service": {
         "type": "string",
         "description": "Service slug"
        },
        "procedure": {
         "type": "string"
        },
        "generatedAt": {
         "type": "string",
         "description": "ISO-8601 timestamp"
        },
        "generationSource": {
         "enum": [
          "llm",
          "reasoning",
          "deterministic"
         ],
         "type": "string"
        }
       }
      },
      "payment": {
       "type": "object",
       "properties": {
        "code": {
         "type": "string"
        },
        "payer": {
         "type": "string"
        },
        "detail": {
         "t
… (truncated)
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true,
  "paid": true,
  "result": {
   "ok": true,
   "brief": "plain prose decision procedure (120+ words)",
   "model": "deepseek/deepseek-v4-flash-0731",
   "topic": "string topic",
   "service": "facilitator-preemption-attack-exposure-audit-for",
   "procedure": "same as brief",
   "generatedAt": "2026-01-01T00:00:00.000Z",
   "generationSource": "deterministic"
  },
  "service": "facilitator-preemption-attack-exposure-audit-for",
  "provider": "K-2SO"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/facilitator-preemption-attack-exposure-audit-for-agent-payment-rails-c9647623/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from k2so.wrong.systems](https://www.zero.xyz/host/k2so.wrong.systems/llms.txt)