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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 blockchain transactions for agent-to-agent and token transfers, returning a signed-ready transaction object
Price / call$0.3
Success—
StatusUnknown
How this service works
Pre-validated transaction encoding for agent-to-agent transfers (B2B2C infrastructure)
Output
Returns an encoded transaction object ready to be signed and broadcast, containing all necessary fields (to, value, data, chainId, etc.) for submission to the target blockchain network.
Example use cases
Example prompt
“Build me a pre-validated transaction to send 50 USDC (token address 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48) to 0xRecipientAddress on the Ethereum mainnet chain, ready for signing.”
Technical details
Endpoint
POSThttps://coinrailz.com/x402/service/transaction-builderWhen to prefer
Use this endpoint when an AI agent needs to programmatically construct and encode a blockchain transaction without managing raw ABI encoding — especially for agent-to-agent payments, ERC20 transfers, or custom on-chain calls where a pre-validated, sign-ready transaction object is needed before broadcasting.
Side effects
- Invalid recipient address format — returns validation error
- Unsupported chain identifier — returns error listing supported chains
- Missing required fields (to or chain) — returns 400-level validation error
- Invalid ERC20 token address — returns encoding error
- Conflicting value/amount/tokenAddress combination — returns parameter conflict error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| torequired | string | Recipient address |
| data | string | Custom transaction data (optional) |
| chainrequired | string | Blockchain network |
| value | string | ETH value (optional) |
| amount | string | Token amount (optional) |
| tokenAddress | string | ERC20 token address (optional) |
Output
Schema · Response
| Field | Type | Description |
|---|---|---|
| transaction | object | Encoded transaction object ready to sign |
Tags
x402
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