Verified contract source (Sourcify)

Fetch the verified Solidity source files and compiler metadata for a contract address from Sourcify's open verification repository. Send POST /api/contract-source with the required field address and pay $0.005 per call over x402 or MPP (there is no free tier). It returns a JSON object with address, network, chainId, verified, match and 4 more.

Covers 8 EVM mainnets (ethereum, base, polygon, arbitrum, optimism, bsc, gnosis, celo). Contracts that were never verified return a structured {verified:false} miss, not an error. Feed the returned source into /api/solidity-scan for a heuristic pattern check.

Category: Crypto & onchain data · Tags: crypto contract smart-contract solidity source verified-source sourcify evm · Also found as: source

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Parameters

Example request

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

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

Example response

{
  "address": "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913",
  "network": "base",
  "chainId": 8453,
  "verified": true,
  "match": "exact_match",
  "verifiedAt": "2024-08-08T13:59:29Z",
  "compiler": {
    "language": "Solidity",
    "version": "0.6.12"
  },
  "sourceCount": 2,
  "sources": {
    "contracts/FiatTokenProxy.sol": "// SPDX-License-Identifier: MIT …"
  }
}

From an MCP client

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

The hosted connector at https://agent402.tools/mcp needs a payment for contract-source; 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-source 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-source", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "address": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "network": "base"
  }),
});

Part of these workflows

Verified contract source (Sourcify) is one step in this skill pack, each sold as a single call:

• Contract audit - Triage a smart contract before an agent interacts with it: verified Solidity source, heuristic vulnerability scan, known-address check, function-selector resolution, and a read-only dry-run of the exact call you plan to make.

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