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On-Chain Transaction Explainer & Payment Verification API
x402
On-Chain Transaction Explainer & Payment Verification API is a paid API for AI agents from freetier-agent-api.pages.dev, paid per call via x402, $0.0025/call, status unknown (last checked 2026-10-30).
Decodes an Ethereum/Base transaction hash into a human-readable JSON summary including transfers, method signatures, gas fees, and optional payment verification checks.
Price / call$0.0025
Success—
StatusUnknown
How this service works
Invoice-to-JSON, on-chain tools (transaction explainer + payment check, wallet profile, contract ABI, ERC-20 token risk), company contacts and web-to-RAG for AI agents. Pay per call with x402 (USDC on Base). No signup, no API key.
Output
Returns a JSON object containing: transaction status (success/failure), sender and recipient addresses, chain name, gas fee in ETH, decoded method selector and human-readable ABI signatures, a list of ERC-20 token transfers with amount/symbol/standard, number of confirmations, and an optional paymentCheck.matched boolean indicating whether the transfer met the specified recipient, token, and amount criteria.
Example use cases
Verify agent payment before fulfilling order
“I need to confirm that transaction 0xabc123...def456 on Base actually sent at least 5 USDC to my wallet address 0x833589fcd6edb6e08f4c7c32d4f71b54bda02913 before I release the digital goods.”
Debug a failed DeFi transaction
“Something went wrong with transaction 0x7f2e...a901 on Ethereum — can you decode it and tell me the method that was called, the status, and what token transfers actually happened?”
Audit payment receipts for an autonomous agent
“My agent just processed a payment and I want to verify that transaction 0xd44b...8812 on Base moved exactly 0.001 USDC and confirm the method signature used — pull the full breakdown for me.”
Technical details
Endpoint
GEThttps://freetier-agent-api.pages.dev/api/tx-explain?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need to decode and explain a specific on-chain transaction by hash, especially when verifying that a crypto payment (USDC, ETH, or other ERC-20) reached the right recipient with the correct amount on Base or Ethereum. It is ideal for AI agent payment workflows using x402, post-payment verification steps, and debugging transaction outcomes. Prefer it over generic block explorers when you need structured JSON output optimized for programmatic consumption at low cost with no API key required.
Side effects
- Invalid or malformed transaction hash returns an error — hash must be 0x followed by 64 hex characters
- Transaction not found on the specified chain returns a not-found error
- Unrecognized or unverified chain value causes a rejection — only 'base' and 'ethereum' are supported
- Payment check fields provided but transfer doesn't match returns paymentCheck.matched: false rather than an error
- Node or RPC timeout may cause a slow or failed response for very recent transactions with low confirmations
- Providing a token symbol not in the supported list without a contract address may fail token resolution
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"to": "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913",
"from": "0x...",
"chain": "base",
"feeEth": "0.0000012",
"method": {
"selector": "0xe3ee160e",
"signatures": [
"transferWithAuthorization(address,address,uint256,uint256,uint256,bytes32,uint8,bytes32,bytes32)"
]
},
"status": "success",
"transfers": [
{
"to": "0x165eb3dc3e98403ecb1141e90400f5e71806554b",
"from": "0x...",
"amount": "0.001",
"symbol": "USDC",
"standard": "erc20"
}
],
"paymentCheck": {
"matched": true
},
"confirmations": 120000
}
}Tags
x402
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