# TraceFast Transaction Storage Writes

> TraceFast Transaction Storage Writes is a paid API for AI agents from mpp.tracefast.xyz, paid per call via x402, $0.1/call, status unknown (last checked 2026-10-19).

Returns every contract storage slot written by an Ethereum transaction, in execution order, including which contract owns the slot, which frame wrote it, the slot key, the new value, and the prior value.

## Facts

- Endpoint: GET https://mpp.tracefast.xyz/api/v1/chains/1/transactions/:hash/storage-writes?utm_source=zero.xyz
- Price: $0.1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-19
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/tracefast-transaction-storage-writes-7df03df1
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_L7CRZEA6noPRsE0-EkICH

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-storage-writes-7df03df1
```

Example prompt: Can you pull all the storage slot writes for Ethereum transaction 0x4a1b...f3c2 — I want to see every contract that got its storage touched, the slot keys, the values written, and what those slots held before the transaction ran?

## When to prefer this

Use this endpoint when you need granular, execution-ordered EVM storage mutation data for a specific transaction — especially when debugging smart contract behavior, auditing delegatecall storage side effects, or reconstructing the exact state diff a transaction produced. Prefer this over event log endpoints when you need raw storage-level changes rather than emitted events, and over block-level state diffs when you need per-transaction, frame-attributed precision including which code address performed each write.

## Known failure modes

- Transaction hash not found or not yet indexed — returns 404 or empty result
- Invalid transaction hash format — returns 400 bad request
- Transaction has no storage writes (e.g. simple ETH transfer) — returns empty list
- Pagination cursor invalid or expired — returns error
- Rate limit or payment failure for the x402 monetized endpoint — returns 402 payment required
- Node data unavailable for pre-archive blocks — partial or missing prior values

## How this service works

TraceFast live Ethereum data: every contract storage slot a transaction wrote, in execution order — which contract's storage, which frame wrote it (with the address whose code ran, which on a `delegatecall` is not the storage owner), the slot, the value written, and the value the slot held before where that can be established. Path: hash. Query: limit, cursor (see docs). Docs: https://docs.tracefast.xyz/api/transaction-storage-writes.md

## Output

A paginated list of storage write events, each containing: the storage-owning contract address, the address whose code ran (the executing frame, which may differ on delegatecall), the storage slot key, the value written to the slot, the value the slot held before the write (where determinable), and the execution order index. Results are ordered by execution sequence within the transaction.

## 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-storage-writes-7df03df1/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)