# Rail Fee Digest

> Rail Fee Digest is a paid API for AI agents from k2so.wrong.systems, paid per call via x402, $0.01/call, status down (last checked 2026-10-31).

Returns a weekly digest of x402/MPP rail economics including per-rail transfer fees, facilitator basis points, live Base gas prices, last-week settlement volumes, and an LLM-composed signal.

## Facts

- Endpoint: GET https://k2so.wrong.systems/api/services/rail-fee-digest?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: down
- Last checked: 2026-10-31
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/rail-fee-digest-a61d94d2
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_BbZTChcZXgILDLnT2HhuP

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 rail-fee-digest-a61d94d2
```

Example prompt: Pull me the latest weekly rail fee digest — I want to see per-rail transfer fees, facilitator basis points, live Base gas, last week's settlement volumes, and the LLM signal on what it all means.

## When to prefer this

Choose this endpoint when you need a structured, regularly-refreshed (weekly) digest of x402/MPP rail economics in a single paid call, especially when you want an LLM-composed signal alongside raw fee and volume data. Prefer this over building your own aggregation when you need facilitator bps, Base gas, settlement volume by rail/facilitator/product, and a synthesized risk/confidence assessment in one response. The 7-day cache ensures freshness without redundant charges.

## Known failure modes

- Payment not processed — returns 402 with payment instructions
- Cache miss on a new week — may incur slightly higher latency for first call of the week
- Invalid days parameter — falls back to default of 7
- meta=1 flag returns free metadata JSON without payment but no digest data
- Network or provider error returns ok:false with error detail

## How this service works

Weekly digest of rail economics for x402/MPP payments: per-rail transfer fees, facilitator bps, live Base gas, last-week settlement volume by rail/facilitator/product, sampled transfer gas, and an LLM-composed signal. Cache is 7 days so each paid call is a fresh weekly read.

## Output

A JSON object with ok/paid status, a result object containing a service slug, an LLM-composed summary, an evidence object, strengths and risk factors arrays, a confidence string, a numerical score, a generatedAt ISO-8601 timestamp, and payment metadata. The digest is cached for 7 days so each paid call returns a fresh weekly read.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "days": {
       "type": "string",
       "default": "7",
       "description": "Composite input. Optional (default: 7)"
      },
      "meta": {
       "enum": [
        "0",
        "1"
       ],
       "type": "string",
       "description": "Set to 1 for free metadata JSON (no payment required)"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "title": "Rail Fee Digest paid response",
     "$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"
        },
        "score": {
         "type": "number"
        },
        "service": {
         "type": "string",
         "description": "Service slug"
        },
        "summary": {
         "type": "string"
        },
        "evidence": {
         "type": "object"
        },
        "strengths": {
         "type": "array",
         "items": {
          "type": "string"
         }
        },
        "confidence": {
         "type": "string"
        },
        "generatedAt": {
         "type": "string",
         "description": "ISO-8601 timestamp"
        },
        "riskFactors": {
         "type": "array",
         "items": {
          "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,
   "service": "rail-fee-digest"
  },
  "service": "rail-fee-digest",
  "provider": "K-2SO"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/rail-fee-digest-a61d94d2/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)