# x402 Pre-flight Transaction Safety Check

> x402 Pre-flight Transaction Safety Check is a paid API for AI agents from x402-services-production.up.railway.app, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).

Analyzes any blockchain transaction before signing and returns a GO/CAUTION/STOP verdict covering success simulation, safety screening, true cost, and wallet balance changes

## Facts

- Endpoint: POST https://x402-services-production.up.railway.app/api/preflight
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-pre-flight-transaction-safety-check-825c4d8f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_0N0bgSigNjITpLdyl06XA

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-pre-flight-transaction-safety-check-825c4d8f -d '<json body>'
```

Example prompt: Before I sign this transaction, run a preflight check on it — simulate whether it'll succeed, flag any drainer or unlimited-approval risks, tell me the true gas cost in USD, and show me exactly how my wallet balances will change.

## When to prefer this

Choose this endpoint when an AI agent or user needs a comprehensive pre-signing safety gate for any blockchain transaction — especially when combining success simulation, security screening, cost estimation, and balance-change prediction in a single call. Prefer it over standalone gas estimators, calldata decoders, or sanctions checkers when you need all four signals at once before committing to a transaction on any EVM-compatible chain.

## Known failure modes

- Transaction object missing required fields — returns validation error
- Chain not supported — returns unsupported chain error
- Node RPC unavailable for the target chain — returns simulation failure
- Contract not verified or self-destructed — limited analysis, may return partial results
- Malformed calldata — returns decode error with partial analysis
- Payment not included or insufficient — returns 402 Payment Required

## How this service works

Pre-Sign Co-Pilot — the ONE call an agent makes before signing ANY transaction, on ANY chain. Returns a single GO/CAUTION/STOP verdict: will it succeed (and if it reverts, why + the exact fix), is it safe (sanctions/drainer/unlimited-approval/rug — hard STOP), true cost (gas + USD), your exact wallet balance-changes after, AND the corrected transac

## Output

A structured verdict (GO, CAUTION, or STOP) along with: success/revert simulation result with revert reason and suggested fix if applicable, safety flags (sanctions, drainer, unlimited approval, rug indicators), true cost breakdown (gas units, gas price, total USD cost), exact wallet balance changes post-execution, and a corrected transaction object if fixes are needed.

## 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"
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json"
     ],
     "type": "string"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-pre-flight-transaction-safety-check-825c4d8f/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-services-production.up.railway.app](https://www.zero.xyz/host/x402-services-production.up.railway.app/llms.txt)