# verify_tx_decode

Independent server-side cross-check of a prepared EVM tx's calldata. Fetches the function signature(s) registered for the 4-byte selector on 4byte.directory (a public registry), re-decodes the calldata via viem against each candidate, and re-encodes to prove the signature describes the exact calldata bytes losslessly. Returns a VerifyDecodeResult whose summary field is pre-written for end-user consumption — the orchestrator should relay it verbatim. Status values: match (independent decode agrees with local ABI), mismatch (function-name disagreement — DO NOT SEND), no-signature / error / not-applicable (no independent check possible; fall back to the swiss-knife URL). On TRON, returns not-applicable — TRON transactions carry no 4-byte selector so this cross-check doesn't apply. Handle is the same opaque ID returned by any prepare_* tool. NEVER do this check by scripting ad-hoc WebFetches to 4byte or swiss-knife; always call this tool so the check runs through a single auditable code path. This is deliberately more expensive than a 4byte-selector lookup — it proves the FULL calldata (not just the function name) is consistent with the independent signature.

Agent View of the PolicyLayer registry record for `verify_tx_decode`. HTML page: https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/verify-tx-decode

## Facts

- Tool: `verify_tx_decode`
- Server: VaultPilot MCP (`vaultpilot-mcp`) — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp.md
- Install: `npx -y vaultpilot-mcp`
- Homepage: https://github.com/szhygulin/vaultpilot-mcp
- Risk category: Read (Low risk)
- Registry record: grade F, identity unverified
- Server rate-limited: no
- Parameters: 1 (1 required)
- Recommended policy verdict: Allowed

## Parameters

| Parameter | Type | Required | Description |
| --- | --- | --- | --- |
| `handle` | string | yes | Opaque handle returned by any prepare_* tool. Use this when the original prepare_* response (and its VERIFY-BEFORE-SIGNING block) has been dropped from your con |

Parameters from the server's own tool schema.

## Example call (MCP tools/call, JSON-RPC 2.0)

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "verify_tx_decode",
    "arguments": {
      "handle": "<handle>"
    }
  }
}
```

## Why verify_tx_decode is rated Low

verify_tx_decode is purely a validation and inspection tool. It decodes and compares transaction calldata against a public registry (4byte.directory) to verify correctness before execution. While it operates on sensitive financial data (crypto transactions), it performs no side effects—no funds move, no state changes, no code execution.

From the tool's own definition: "Tool performs 'Independent server-side cross-check' and 'Fetches the function signature(s)' and 're-decodes the calldata' — all read-only verification operations. Returns a VerifyDecodeResult with status values like 'match', 'mismatch', 'no-signature'."

## Use case

AI agents call verify_tx_decode to retrieve information from VaultPilot MCP without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.

## Recommended policy (PolicyLayer)

Verdict: **Allowed**. Enforced by the PolicyLayer MCP gateway (https://policylayer.com/mcp-gateway) before a call reaches VaultPilot MCP:

```json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "verify_tx_decode": {}
  }
}
```

## Other tools on VaultPilot MCP (188)

- `prepare_btc_lifi_swap` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-btc-lifi-swap.md
- `prepare_btc_rbf_bump` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-btc-rbf-bump.md
- `prepare_jito_stake` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-jito-stake.md
- `prepare_marginfi_init` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-marginfi-init.md
- `prepare_solana_nonce_close` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-solana-nonce-close.md
- `prepare_sunswap_swap` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-sunswap-swap.md
- `prepare_uniswap_v3_burn` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-uniswap-v3-burn.md
- `prepare_uniswap_v3_mint` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-uniswap-v3-mint.md
- `remove_contact` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/remove-contact.md
- `unregister_btc_multisig_wallet` — Destructive — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/unregister-btc-multisig-wallet.md
- `combine_btc_psbts` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/combine-btc-psbts.md
- `pair_ledger_btc` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/pair-ledger-btc.md
- `prepare_aave_repay` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-aave-repay.md
- `prepare_btc_multisig_send` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-btc-multisig-send.md
- `prepare_compound_repay` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-compound-repay.md
- `prepare_compound_supply` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-compound-supply.md
- `prepare_curve_swap` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-curve-swap.md
- `prepare_custom_call` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-custom-call.md
- `prepare_kamino_init_user` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-kamino-init-user.md
- `prepare_kamino_supply` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-kamino-supply.md
- `prepare_lido_unstake` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-lido-unstake.md
- `prepare_lido_unwrap` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-lido-unwrap.md
- `prepare_lido_wrap` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-lido-wrap.md
- `prepare_native_stake_deactivate` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-native-stake-deactivate.md
- `prepare_native_stake_delegate` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-native-stake-delegate.md
- `prepare_rocketpool_unstake` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-rocketpool-unstake.md
- `prepare_safe_tx_execute` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-safe-tx-execute.md
- `prepare_solana_lifi_swap` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-solana-lifi-swap.md
- `prepare_solana_nonce_init` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-solana-nonce-init.md
- `prepare_solana_swap` — Execute — https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp/prepare-solana-swap.md
- …and 158 more: https://policylayer.com/tools/io-github-szhygulin-vaultpilot-mcp.md

## For agents

This record is a snapshot. Live verdicts and the full registry:

- Check every server in your MCP config at once: `npx -y policylayer stack`
- Vet a server before you add it: install the mcp-precheck skill — `npx skills add https://policylayer.com` (skill text: https://policylayer.com/skill.md)
- Query the registry over MCP: endpoint `https://api.policylayer.com/mcp` — tools `check_mcp_server`, `check_mcp_stack`, `check_tool`, `search_registry`, `get_change_events`

---

Source: the PolicyLayer MCP registry — one continuously verified record per MCP server. Full record: https://policylayer.com/registry?q=io-github-szhygulin-vaultpilot-mcp · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/io-github-szhygulin-vaultpilot-mcp