prepare_revoke_approval

SERVERVaultPilot MCP SOURCEvaultpilot-mcp

Medium RISK CLASS

Category Write

Parameters 43 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/io-github-szhygulin-vaultpilot-mcp/prepare-revoke-approval.md

WHAT IT DOES

What prepare_revoke_approval does on VaultPilot MCP

AI agents use prepare_revoke_approval to create or update resources in VaultPilot MCP, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your VaultPilot MCP environment.

Parameter	Type	Required	Description
`chain`	string	—
`token`	string	Yes	ERC-20 contract address. Must be the actual token contract — wrappers and aTokens have their own approval surfaces and aren't supported here.
`wallet`	string	Yes	EVM wallet that owns the existing allowance. Must be the address that originally called approve(spender, value); only the owner can set the allowance back to ze
`spender`	string	Yes	Address whose allowance to revoke. Typically a protocol contract (Aave V3 Pool, Uniswap SwapRouter, etc.) or any EOA the user previously approved. Get the live

Parameters from the server's own tool schema.

RISK

Why prepare_revoke_approval is rated Medium

This tool constructs a token approval transaction setting allowance to zero, which is a reversible on-chain write operation (the allowance can be re-granted later). It does not delete or destroy assets, nor does it move funds — it only modifies a smart contract allowance state. The transaction is unsigned at this stage, requiring a separate signing/broadcast step.

From the tool's definition Build an unsigned `approve(spender, 0)` transaction that revokes the allowance the wallet previously granted to `spender` on `token`

Risk signalsHandles credentials or secrets (token)

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs prepare_revoke_approval safely

PolicyLayer is an MCP gateway: it sits between your AI agents and VaultPilot MCP, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For prepare_revoke_approval, this is the rule to start with:

prepare_revoke_approval Rate-limited

prepare_revoke_approval stays usable, but capped: an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "prepare_revoke_approval": {
      "limits": [
        {
          "counter": "prepare_revoke_approval_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect VaultPilot MCP, apply this rule, and every prepare_revoke_approval call is checked against it from then on.

FAQ

Questions about prepare_revoke_approval

What does the prepare_revoke_approval tool do? +

Build an unsigned approve(spender, 0) transaction that revokes the allowance the wallet previously granted to spender on token. Pre-flight check refuses when the live allowance is already 0 — that call would burn gas for nothing, and almost certainly means the user named the wrong (token, spender) pair. Resolves a friendly spender label from the canonical CONTRACTS table when one matches (Aave V3 Pool, Uniswap V3 SwapRouter02, Lido stETH, Compound V3 cUSDCv3, Morpho Blue, etc.) so the description + Ledger preview reads as "Revoke USDC allowance for Aave V3 Pool (0x...)" instead of a raw hex address. Description includes the previous allowance amount so the user sees what's being zeroed out. EVM-only — TRC-20 has the same approve(spender, value) shape but its prepare path runs through the TRON builder pipeline; surface in a prepare_tron_trc20_revoke if asked. Pair with the read-side get_token_allowances to enumerate what's currently approved. It is categorised as a Write tool in the VaultPilot MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

What parameters does prepare_revoke_approval accept? +

prepare_revoke_approval accepts 4 parameters: chain, token, wallet, spender. Required: token, wallet, spender. The full parameter table on this page comes from the server's own tool schema.

How do I enforce a policy on prepare_revoke_approval? +

Register the VaultPilot MCP server in PolicyLayer and add a rule for prepare_revoke_approval: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches VaultPilot MCP. Nothing to install.

What risk level is prepare_revoke_approval? +

prepare_revoke_approval is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit prepare_revoke_approval? +

Yes. Add a rate_limit block to the prepare_revoke_approval rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block prepare_revoke_approval completely? +

Set action: deny in the PolicyLayer policy for prepare_revoke_approval. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides prepare_revoke_approval? +

prepare_revoke_approval is provided by the VaultPilot MCP server (vaultpilot-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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