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Coin Railz Transaction Builder
x402
Coin Railz Transaction Builder is a paid API for AI agents from coinrailz.com, paid per call via x402, $0.3/call, status unknown (last checked 2026-09-15).
Encodes and pre-validates crypto transfer transactions for agent-to-agent (B2B2C) payment flows before submission to the blockchain
Price / call$0.3
Success—
StatusUnknown
How this service works
Pre-validated transaction encoding for agent-to-agent transfers (B2B2C infrastructure)
Output
Returns a JSON object containing the encoded transaction payload ready for signing, a success flag, the service name ('transaction-builder'), and a timestamp. The agent receives a structured transaction object it can directly sign and submit to the target blockchain network.
Example use cases
Autonomous agent-to-agent payment settlement
“Set up a pre-validated transaction so my service agent can automatically pay vendor agents 0.5 ETH each time they complete a task, all ready to sign and broadcast to Ethereum mainnet.”
DeFi bot token swap preparation
“Build me an encoded transaction payload to swap 100 USDC for DAI on Uniswap before my trading bot signs it, I want the validated payload back first.”
Batch crypto payroll for agent fleet
“Generate pre-validated transaction objects to distribute weekly USDC payments to my 10 deployed agents across different wallets on Polygon, so they can each sign and settle autonomously.”
Technical details
Endpoint
POSThttps://coinrailz.com/x402/transaction-builderWhen to prefer
Choose this endpoint when your agent needs to programmatically construct and pre-validate a blockchain transaction before signing — especially for autonomous agent-to-agent (B2B2C) payment pipelines where pre-validation reduces broadcast failures. Prefer this over raw RPC calls when you want a structured, validated transaction object returned as JSON without handling raw ABI encoding yourself.
Side effects
- Invalid sender or recipient address format returns validation error
- Unsupported chain ID results in error response
- Missing required fields (amount, token, addresses) causes 400-level error
- Insufficient USDC balance to pay the $0.30 per-call fee blocks the request
- Malformed token contract address triggers encoding failure
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| query | string | Query parameter for the service |
Output
Schema · Response
{
"type": "application/json",
"format": "json",
"example": {
"result": "Service executed successfully",
"service": "transaction-builder",
"success": true,
"timestamp": "2026-02-07T01:42:05.861Z"
}
}Tags
x402
Reviews
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