{"uid":"cap_2EvvMsCRebNvEqd3RIOV2","slug":"coin-railz-transaction-builder-2429dfee","name":"Coin Railz Transaction Builder","description":"Pre-validated transaction encoding for agent-to-agent transfers (B2B2C infrastructure)","url":"https://coinrailz.com/x402/service/transaction-builder","method":"POST","headers":{},"bodySchema":{"type":"object","required":["to","chain"],"properties":{"to":{"type":"string","description":"Recipient address"},"data":{"type":"string","description":"Custom transaction data (optional)"},"chain":{"type":"string","description":"Blockchain network"},"value":{"type":"string","description":"ETH value (optional)"},"amount":{"type":"string","description":"Token amount (optional)"},"tokenAddress":{"type":"string","description":"ERC20 token address (optional)"}}},"responseSchema":{"type":"object","properties":{"transaction":{"type":"object","description":"Encoded transaction object ready to sign"}}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.3","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.3/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.3","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.3","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_H0jH2foT05zbkIneuS5ND","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.3","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Encodes and pre-validates blockchain transactions for agent-to-agent and token transfers, returning a signed-ready transaction object","exampleAgentPrompt":"Build me a pre-validated transaction to send 50 USDC (token address 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48) to 0xRecipientAddress on the Ethereum mainnet chain, ready for signing.","exampleUseCases":null,"resultDescription":"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.","failureModes":["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"],"whenToPreferThis":"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.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-15T18:42:09.678Z","isFirstParty":false}