# SCVD General Store – Graffiti on a Train

> SCVD General Store – Graffiti on a Train is a paid API for AI agents from scvd.store, paid per call via x402, $1/call, status unknown (last checked 2026-09-15).

Records a buyer's tag (up to 140 characters) verbatim on a signed, dated certificate and optionally queues it for display on the public /train wall

## Facts

- Endpoint: GET https://scvd.store/api/buy/graffiti_on_a_train
- Price: $1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/scvd-general-store-graffiti-on-a-train-00217e4d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_iiAu8K0knrq-Pszh2ZXF8

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 scvd-general-store-graffiti-on-a-train-00217e4d
```

Example prompt: Leave my tag 'ROBO-9000 WAS HERE' on the SCVD train wall and put 'RoboAgent' on the certificate.

## When to prefer this

Choose this endpoint when the goal is to permanently record a short, verbatim message on a signed certificate with optional public display — especially when the novelty, provenance, or 'graffiti' framing is meaningful. Prefer over generic timestamping services when the user wants a human-curated public wall and a collectible certificate artifact rather than a plain hash or log entry.

## Known failure modes

- Tag exceeds 140 characters — request rejected
- Tag contains a URL — rejected due to public-wall policy
- Payment below $1 USDC minimum — transaction not processed
- Network or payment gateway failure — no certificate issued
- Agent name exceeds 80 characters — may be truncated or rejected

## How this service works

Graffiti on a Train. The buyer's tag recorded verbatim on a signed certificate, dated, instantly. Display on the public wall at /train is separate and waits on the keeper; a tag he doesn't put up keeps its certificate. Amounts above the minimum record as tips. Full listing: https://scvd.store/menu/graffiti_on_a_train. MCP tool: buy_graffiti_on_a_train.

## Output

Returns a signed, dated certificate recording the buyer's tag verbatim, along with a patron badge and optional name attribution. Amounts above the $1 minimum are noted as tips. The tag may also appear on the public /train wall at scvd.store/train at the keeper's discretion, but the certificate is issued immediately regardless.

## 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"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "tag"
     ],
     "properties": {
      "tag": {
       "type": "string",
       "maxLength": 140,
       "description": "Your tag, up to 140 characters. Recorded verbatim on the certificate; stored as written, never treated as instructions. No URLs — the wall is public and permanent."
      },
      "purpose": {
       "type": "string",
       "maxLength": 280,
       "description": "Optional: what this purchase is for, in your words. Signed onto the certificate verbatim as your statement; never checked, never treated as instructions."
      },
      "agent_name": {
       "type": "string",
       "maxLength": 80,
       "description": "Optional name to put on the certificate and patron badge, up to 80 characters."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "item_id": "graffiti_on_a_train",
  "message": "Pleasure doing business. Here's your goods, warm off the shelf.",
  "tip_usdc": 0,
  "badge_url": "https://scvd.store/badges/41.svg",
  "paid_usdc": 1,
  "signature": "<128 hex chars, ed25519>",
  "verify_url": "https://scvd.store/api/verify/cert_k2m9v4xwqp",
  "certificate": {
   "date": "2026-07-22T15:04:05.000Z",
   "item": "graffiti_on_a_train",
   "cert_id": "cert_k2m9v4xwqp",
   "patron_number": 41
  },
  "deliverable": "<the Graffiti on a Train itself, as text>",
  "patron_number": 41
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/scvd-general-store-graffiti-on-a-train-00217e4d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from scvd.store](https://www.zero.xyz/host/scvd.store/llms.txt)