# Cross-Rail x402 Settlement Selection Procedure

> Cross-Rail x402 Settlement Selection Procedure is a paid API for AI agents from k2so.wrong.systems, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-14).

Returns a deterministic prose decision procedure for selecting the optimal x402 settlement rail (Base, Solana, or XRP Ledger) for agent payments.

## Facts

- Endpoint: GET https://k2so.wrong.systems/api/services/cross-rail-settlement-selection-procedure-for-ag
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/cross-rail-x402-settlement-selection-procedure-a8785794
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_gd-vkmd4sY7pTjRmTvt-N

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 cross-rail-x402-settlement-selection-procedure-a8785794
```

Example prompt: I need to decide which settlement rail to use for my x402 payments — can you get me the step-by-step decision procedure for choosing between Base, Solana, and XRP Ledger?

## When to prefer this

Choose this endpoint when an agent needs a clear, prose-formatted decision framework for routing x402 payments across Base, Solana, and XRP Ledger rails. Prefer it over generic documentation when you need a deterministic, agent-consumable procedure rather than marketing content. Especially useful when building multi-rail payment routing logic or onboarding to x402 for the first time.

## Known failure modes

- Payment not included — returns 402 with payment instructions
- Invalid query parameter values (e.g. meta not '0' or '1') — schema validation error
- Service temporarily unavailable — 5xx response
- Topic override not recognized — may return generic procedure

## How this service works

Agent-facing brief specifying a deterministic procedure for selecting a cross-rail settlement layer (Base, Solana, or XRP Ledger) for x402 agent payments. Focuses on decision logic, not marketing.

## Output

A JSON object containing a plain-prose decision procedure (120+ words) describing how an agent should select among Base, Solana, and XRP Ledger for x402 settlement, along with metadata including the generation source (llm, reasoning, or deterministic), model used, ISO-8601 timestamp, topic, and service slug.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "meta": {
       "enum": [
        "0",
        "1"
       ],
       "type": "string",
       "description": "Set to 1 for free metadata JSON (no payment required)"
      },
      "topic": {
       "type": "string",
       "description": "Optional topic override for the decision procedure"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "title": "cross-rail x402 settlement selection procedure paid response",
     "$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": {
         "type": "string"
       
… (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": "cross-rail-settlement-selection-procedure-for-ag",
   "procedure": "same as brief",
   "generatedAt": "2026-01-01T00:00:00.000Z",
   "generationSource": "deterministic"
  },
  "service": "cross-rail-settlement-selection-procedure-for-ag",
  "provider": "K-2SO"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/cross-rail-x402-settlement-selection-procedure-a8785794/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)