# Coin Railz Token Approval Transaction Generator

> Coin Railz Token Approval Transaction Generator is a paid API for AI agents from coinrailz.com, paid per call via x402, $0.2/call, status unknown (last checked 2026-09-13).

Generates ERC-20 token approval transactions for DeFi agents to authorize a spender (e.g. DEX router) to spend a specified amount of a given token on a blockchain network

## Facts

- Endpoint: POST https://coinrailz.com/x402/service/approval-manager
- Price: $0.2/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/coin-railz-token-approval-transaction-generator-f183bdb2
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_6boynH_KdR-GoFqHzXPQ8

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 coin-railz-token-approval-transaction-generator-f183bdb2 -d '<json body>'
```

Example prompt: Generate a token approval transaction on Ethereum to let the Uniswap v3 router (0xE592427A0AEce92De3Edee1F18E0157C05861564) spend up to 500 USDC (token address 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48) on my behalf.

## When to prefer this

Use this endpoint when an AI agent needs to programmatically construct an ERC-20 token approval (allowance) transaction before executing a DeFi swap or interaction that requires a prior approve() call. Prefer this over manually encoding approve() calldata when you need a ready-to-broadcast transaction object for a specific chain and spender without managing ABI encoding yourself.

## Known failure modes

- Invalid or unrecognized chain identifier — returns error indicating unsupported network
- Malformed token address or spender address — returns validation error
- Amount value not parseable (must be numeric string or 'unlimited') — returns parsing error
- Payment failure (insufficient USDC for $0.2 fee) — returns 402 Payment Required
- Missing required fields (chain, amount, spender, tokenAddress) — returns 400 Bad Request

## How this service works

Token approval transaction generator - required infrastructure for DeFi agents (B2B2C infrastructure)

## Output

Returns an approvalTransaction object containing the full transaction data (to, data, value, etc.) needed to submit an ERC-20 approve() call on-chain, authorizing the specified spender to transfer up to the given amount of the token.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "chain",
  "amount",
  "spender",
  "tokenAddress"
 ],
 "properties": {
  "chain": {
   "type": "string",
   "description": "Blockchain network"
  },
  "amount": {
   "type": "string",
   "description": "Amount to approve or 'unlimited'"
  },
  "spender": {
   "type": "string",
   "description": "Spender address (DEX router)"
  },
  "tokenAddress": {
   "type": "string",
   "description": "Token to approve"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "approvalTransaction": {
   "type": "object",
   "description": "Approval transaction data"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/coin-railz-token-approval-transaction-generator-f183bdb2/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from coinrailz.com](https://www.zero.xyz/host/coinrailz.com/llms.txt)