Why a transaction reverted

Open this transaction in TraceFast →

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 and so on — the revert payload with its selector, and the error name when the selector is known. Root frame first, then nested frames in tree order, at most 100.

GET https://tracefast.xyz/api/v1/chains/1/transactions/{hash}/failures

Access — an API key on the Enriched Data plan or higher (plans), or no key at all: pay per call with x402 at the same path on https://mpp.tracefast.xyz/api/v1, at the price its 402 states. As a tool for AI agents: get_transaction_failures on the MCP server. Stable — see stability.

chains/1 is a literal: the method serves Ethereum mainnet data. Other chain ids answer 404 chain_not_supported. There are no query parameters — an unknown one is refused rather than ignored.

What it covers, and what it does not

• Only the frames that failed. A transaction can succeed while an inner call reverts and is caught; the whole call tree, successes included, is the execution trace.
• An empty list is "no failure recorded", never "succeeded". A successful transaction answers an empty list, and so does a hash that is not known at all — frameCount: 0 in both cases. For the outcome, read status on one transaction.
• A transaction the failure classification has not reached is refused, not answered empty. The classification trails the chain by minutes to hours. A known transaction in a block they have not reached answers 422 block_not_available with reason: coverage_gap and maxAvailableBlock, the last block classified — an empty list there would read as success. It says nothing about the outcome; ask again later — see data freshness.
• At most 100 frames. framesTruncated says when there are more; frames is then a prefix in tree order.

Response

200 application/json:

{
  "data": {
    "chainId": 1,
    "hash": "0xd1bed4098b76c7c1c064db3ab687325643cebb82abca705ae24d7f75021f1d05",
    "blockNumber": 25920002,
    "frameCount": 1,
    "framesTruncated": false,
    "frames": [
      {
        "callPath": "0000",
        "callDepth": 1,
        "callType": "CALL",
        "from": "0x34f41c98898ed0c2f7d004538a7cbde33b35404f",
        "to": "0xde7034b494cc4fc2479b4605c1b6e56d4a1c6154",
        "errorKind": "CustomError",
        "status": "Revert",
        "revertSelector": "0xc64fc372",
        "errorName": "Err",
        "errorSignature": "Err()",
        "revertData": "0xc64fc372",
        "revertDataTruncated": false,
        "revertDataLength": 4,
        "gasUsed": 3008
      }
    ]
  },
  "meta": {
    "chain": "ethereum",
    "timestamp": 1789063644369,
    "cached": false,
    "asOfBlock": 25920002,
    "docs": "https://docs.tracefast.xyz/api/transaction-failures"
  }
}

The top-level call reverted with the contract's custom error Err(): its four-byte selector is the whole payload.

data

A failed frame

Errors

An unknown hash is not an error here — it answers an empty list.

A recent transaction the classification has not reached:

{
  "error": {
    "code": "block_not_available",
    "message": "the failure classification of block 25948674 is not available yet: it is available up to block 25925050. This says nothing about the transaction's outcome — retry later, or ask about a transaction at or below block 25925050.",
    "details": {
      "reason": "coverage_gap",
      "maxAvailableBlock": 25925050,
      "coverageGapFromBlock": 25925051
    }
  }
}

Malformed input, unknown parameters and the key check's 401/403/429 are the same for every method — see conventions and API keys.

Related pages

• Execution trace of a transaction — the full call tree, caught reverts included
• One transaction — the outcome, in status
• Function selectors of a contract — what the target exposes
• Transactions — the transaction page in the app

Last updated 22 Oct 2026, 08:06 UTC · verified against TraceFast v1.0.261 · Markdown