Verified contract ABI (Sourcify)

Fetch the verified ABI for a contract address from Sourcify, plus a ready-to-use list of human-readable function signatures with their 4-byte selectors. Send POST /api/contract-abi with the required field address and pay $0.003 per call over x402 or MPP (there is no free tier). It returns a JSON object with address, network, chainId, verified, match and 3 more.

Covers 8 EVM mainnets. Unverified contracts return a structured {verified:false} miss. Pair with /api/calldata-decode to decode transactions against this ABI.

Category: Crypto & onchain data · Tags: crypto contract smart-contract abi sourcify evm selector · Also found as: contract

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Parameters

Example request

curl -i -X POST https://agent402.tools/api/contract-abi \
  -H "Content-Type: application/json" \
  -d '{"address":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","network":"base"}'

Without payment this returns HTTP 402 Payment Required with the exact price for contract-abi; any x402 v2 or MPP client pays it and retries.

Example response

{
  "address": "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913",
  "network": "base",
  "chainId": 8453,
  "verified": true,
  "match": "exact_match",
  "abi": [
    {
      "name": "implementation",
      "type": "function",
      "inputs": [],
      "outputs": [
        {
          "type": "address"
        }
      ]
    }
  ],
  "functions": [
    {
      "signature": "implementation()",
      "selector": "0x5c60da1b"
    }
  ],
  "events": [
    {
      "signature": "Upgraded(address)"
    }
  ]
}

From an MCP client

catalog.call {
  "slug": "contract-abi",
  "params": {
    "address": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "network": "base"
  }
}

The hosted connector at https://agent402.tools/mcp needs a payment for contract-abi; the stdio package pays it from a wallet or from AGENT402_CREDITS_KEY. Local install: npx -y agent402-mcp.

Errors and behavior

• address is required. An input the tool rejects returns an HTTP 4xx whose body carries error, tool, expected, required and example, so the caller can correct it.
• A paid call that ends in any status of 400 or above is not charged over x402, MPP or a prepaid credits key: settlement is cancelled when the tool fails. The exception is a Tempo push credential, a transfer the buyer sent before the call: it settles before the tool runs, so if the tool then fails the payment is recorded as a refund owed to the paying wallet.
• Wallet-only: this tool reaches the network or stored state, so it has no proof-of-work tier. A prepaid card-credits key issued earlier (Authorization: Bearer a402_...) also pays it.
• A GET or HEAD to /api/contract-abi returns the same 402 quote, so the price can be read without a body.
• An Idempotency-Key header makes a retried paid call replay the first 200 instead of charging again (an answer larger than 1 MB is not replayed).

Paid call (JavaScript agent)

import { wrapFetchWithPayment } from "@x402/fetch";
import { x402Client } from "@x402/core/client";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const client = new x402Client();
client.setSpendControls?.(false); // keep your own spending ceiling in code
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/contract-abi", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "address": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "network": "base"
  }),
});

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