# TraceFast Transaction Failures

> TraceFast Transaction Failures is a paid API for AI agents from mpp.tracefast.xyz, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-12).

Returns all failed call frames within a reverted Ethereum transaction, including their position in the call tree, caller/target addresses, failure kind, revert payload, and decoded error name.

## Facts

- Endpoint: GET https://mpp.tracefast.xyz/api/v1/chains/1/transactions/:hash/failures?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-12
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/tracefast-transaction-failures-ccfc4de3
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_UGpQU9LOgx5Os2hb1GFH5

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 tracefast-transaction-failures-ccfc4de3
```

Example prompt: Can you tell me exactly why transaction 0x4e3a7c2f1b8d6e0a9f5c3b2d7e1a4f8c6b0d3e9a7f5c2b1d8e6a0f3c7b4d9e2a failed on Ethereum — which call frames reverted, what kind of failure it was, and what the decoded error name is?

## When to prefer this

Choose this endpoint when you need to debug or analyze a specific reverted Ethereum transaction and want structured, decoded failure information for every failed call frame — especially when you need to distinguish between revert types (custom error, panic, out of gas) and decode error selectors into human-readable names. Prefer this over generic RPC trace calls when you need pre-processed, structured failure data without parsing raw trace output yourself.

## Known failure modes

- Invalid or malformed transaction hash returns a 400 error
- Transaction hash not found on Ethereum mainnet returns a 404
- Transaction that succeeded (not reverted) may return an empty failure list
- Network or RPC issues may cause intermittent 500 errors
- Payment not included or insufficient USDC via x402 protocol returns 402

## How this service works

TraceFast live Ethereum data: the failed call frames of a reverted transaction — for each, its position in the call tree, caller and target, the kind of failure (revert, panic, custom error, out of gas, …), the revert payload with its selector, and the error name when the selector is known. Path hash: Transaction hash, `0x`-prefixed, 64 hex characters, any case. Docs: https://docs.tracefast.xyz/api/transaction-failures.md

## Output

A list of failed call frames from the reverted transaction, each containing: its position in the call tree, the caller and target contract addresses, the type of failure (revert, panic, custom error, out of gas, etc.), the raw revert payload with its 4-byte selector, and the human-readable error name when the selector is recognized.

## Request schema (JSON Schema)

```json
{
 "properties": {
  "input": {
   "required": [
    "method"
   ],
   "properties": {
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "pathParams": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/tracefast-transaction-failures-ccfc4de3/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from mpp.tracefast.xyz](https://www.zero.xyz/host/mpp.tracefast.xyz/llms.txt)