# Vextorium ERC-20 Approval Revocation Transaction Builder

> Vextorium ERC-20 Approval Revocation Transaction Builder is a paid API for AI agents from api.vextorium.com, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-16).

Builds the unsigned transaction calldata to revoke a spender's ERC-20 token approval (approve(spender, 0)) — ready to sign and broadcast, nothing is sent on-chain.

## Facts

- Endpoint: POST https://api.vextorium.com/revocar-aprobacion-pago?utm_source=zero.xyz
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-16
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/vextorium-erc-20-approval-revocation-transaction-builder-6a83390f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_XkhFk0oaRtpPBbfhibqBg

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 vextorium-erc-20-approval-revocation-transaction-builder-6a83390f -d '<json body>'
```

Example prompt: Build me the transaction to revoke the spending approval that 0x2626664c2603336E57B271c5C0b26F421741e481 has over my USDC token at 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 — I want the calldata ready to sign in my wallet.

## When to prefer this

Choose this endpoint when you need to programmatically construct a revoke-approval transaction without connecting a wallet to a UI. Ideal for agents automating wallet security workflows, post-exploit remediation bots, or any flow that needs raw calldata for approve(spender, 0) on ERC-20 tokens deployed on EVM chains like Base or Ethereum. Prefer this over manual ABI encoding when you want a simple, paid REST call that returns ready-to-sign target + calldata.

## Known failure modes

- Invalid or malformed token address returns an error
- Invalid or malformed spender (gastador) address returns an error
- Non-ERC-20 contract address may produce calldata that reverts on-chain
- Network errors or upstream timeout return a 5xx response
- Missing required fields (token or gastador) return a 400-level validation error

## How this service works

Build the transaction that revokes a contract's permission over an ERC-20 token (approve(spender, 0)): target and calldata ready to sign in your wallet. Nothing is sent.

## Output

A JSON object containing: the target token contract address (`para`), the full hex-encoded calldata (`datos`) for approve(address,uint256) with amount=0, the ETH value to send (always '0'), the function signature string, the decoded arguments array, and a human-readable note reminding the user to sign and send the transaction from the wallet that originally granted the permission.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "token": {
   "type": "string"
  },
  "gastador": {
   "type": "string"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "nota": "Firma y envía esta transacción desde la wallet que dio el permiso.",
  "para": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
  "datos": "0x095ea7b30000000000000000000000002626664c2603336e57b271c5c0b26f421741e4810000000000000000000000000000000000000000000000000000000000000000",
  "valor": "0",
  "funcion": "approve(address,uint256)",
  "argumentos": [
   "0x2626664c2603336E57B271c5C0b26F421741e481",
   "0"
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/vextorium-erc-20-approval-revocation-transaction-builder-6a83390f/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.vextorium.com](https://www.zero.xyz/host/api.vextorium.com/llms.txt)