# x402 Transaction Watch

> x402 Transaction Watch is a paid API for AI agents from x402-gateway-production-1f21.up.railway.app, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-10).

Monitors a blockchain transaction by hash and detects state changes, returning a deterministic status snapshot for Base or Ethereum networks.

## Facts

- Endpoint: POST https://x402-gateway-production-1f21.up.railway.app/agent/transaction-watch?utm_source=zero.xyz
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-10
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-transaction-watch-439e7315
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_oEd60Jow8cdpMkHIDaevC

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 x402-transaction-watch-439e7315 -d '<json body>'
```

Example prompt: Watch transaction 0xabc123...def456 on Base and let me know if its state has changed since the last time we checked — the previous state hash was 9f3c...a1b2.

## When to prefer this

Choose this endpoint when you need deterministic, hash-based change detection for a specific transaction on Base or Ethereum — particularly in agentic pipelines where you need to poll or compare state over time without duplicating logic. Prefer it over generic block explorers when you need a machine-payable, structured API response rather than a human-facing UI, and when you already have a previous state hash to compare against.

## Known failure modes

- Invalid tx_hash format (must be 0x-prefixed 64 hex chars) returns validation error
- Invalid previous_state_hash format returns schema error
- Unsupported network value (not 'base' or 'ethereum') rejected by enum constraint
- Transaction not yet indexed or not found on the specified network
- Payment failure or insufficient USDC balance blocks the x402-gated request
- Network timeout if the RPC node is slow to respond

## How this service works

Transaction confirmation watch primitive for autonomous agents. Check whether an EVM transaction is pending, confirmed or reverted and return confirmations plus next-check state. Supply previous_state_hash on later polls to detect status changes without keeping server-side state.

## Output

Returns a JSON object with a 'status' field (e.g. 'ready') indicating the current state of the monitored transaction, enabling the caller to detect whether the on-chain state has changed relative to a previously recorded hash.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "type": "object",
     "required": [
      "tx_hash"
     ],
     "properties": {
      "network": {
       "enum": [
        "base",
        "ethereum"
       ],
       "type": "string",
       "default": "base"
      },
      "tx_hash": {
       "type": "string",
       "pattern": "^0x[a-fA-F0-9]{64}$"
      },
      "previous_state_hash": {
       "type": "string",
       "pattern": "^[a-fA-F0-9]{64}$"
      }
     },
     "additionalProperties": false
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "status": "ready"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-transaction-watch-439e7315/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-gateway-production-1f21.up.railway.app](https://www.zero.xyz/host/x402-gateway-production-1f21.up.railway.app/llms.txt)