# Live Per-Rail Fee Index for x402 Settlement Choice

> Live Per-Rail Fee Index for x402 Settlement Choice is a paid API for AI agents from k2so.wrong.systems, paid per call via x402, $0.002/call, status down (last checked 2026-09-14).

Returns current fee schedules across Base, Solana, MPP/Tempo, and fee-free rails (Open USD) for x402 payments, with freshness timestamps and a recommended cheapest-rail verdict.

## Facts

- Endpoint: GET https://k2so.wrong.systems/api/services/live-per-rail-fee-index-for-x402-settlement-choi
- Price: $0.002/call
- Payment: x402
- Status: down
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/live-per-rail-fee-index-for-x402-settlement-choice-c02c69d7
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_bprXvZkWL6pPQ72aAOvCV

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 live-per-rail-fee-index-for-x402-settlement-choice-c02c69d7
```

Example prompt: Can you pull the current fee index for x402 rails and tell me which one — Base, Solana, MPP/Tempo, or Open USD — is the cheapest option for settling a stablecoin payment right now?

## When to prefer this

Prefer this endpoint when an AI agent needs to make a real-time, cost-optimal routing decision for x402 payments across multiple rails and requires a single authoritative verdict rather than assembling fee data from multiple sources. Especially useful for automated payment routing pipelines where the agent cannot afford to query each rail separately. Choose alternatives if you need raw blockchain fee data without the decision layer, or if you are not using x402 as your payment protocol.

## Known failure modes

- Payment not completed — endpoint requires $0.002 USDC x402 payment; unpaid requests return 402 Payment Required
- Stale fee data if underlying rail oracles are unavailable — freshness timestamp indicates data age
- Invalid topic override parameter results in default topic being used
- LLM generation failure returns ok:false with error detail in result
- Network timeout from k2so.wrong.systems may result in no response

## How this service works

Paid agent-facing brief on Live per-rail fee index for x402 settlement choice: current fee schedules (stablecoin transfer fee, facilitator/merchant fee, L2 gas for the rail) across Base, Solana, MPP/Tempo, and fee-free rails like Open USD, with freshness timestamps and a recommended cheapest rail verdict. Blunt decision procedure, not marketing.

## Output

A paid brief containing current fee schedules for each x402 rail (Base, Solana, MPP/Tempo, Open USD) including stablecoin transfer fees, facilitator/merchant fees, and L2 gas costs, along with ISO-8601 freshness timestamps and a blunt cheapest-rail recommendation. Response includes ok/paid status flags, service slug, provider, and generation metadata.

## Request schema (JSON Schema)

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

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/live-per-rail-fee-index-for-x402-settlement-choice-c02c69d7/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)