Decode an EVM smart contract. Pass chain (ethereum, base, polygon, arbitrum, optimism, bsc, avalanche) + address; returns whether the contract is source-verified (Sourcify), its name/compiler/language, whether it is a proxy and its implementation address, and human-readable function and event signatures from the ABI. Optionally pass selector (a 0x 4-byte function selector) to decode what it calls — resolved from the contract's own ABI when verified, otherwise from the public 4byte directory. Pairs with crypto.tx (which gives a `to` address + calldata): turn an opaque contract + selector into "what is this and what does it do." Free, keyless.
/api/crypto/contractPAYMENT-SIGNATURE.The contract API is a pay-per-call crypto endpoint built for AI agents and autonomous software. Decode an EVM smart contract.
There is no signup and no API key. An agent (or any HTTP client) hits the endpoint, receives an x402 "402 Payment Required" challenge, signs a sub-cent USDC payment on Base or Solana, and retries — the data comes back on the paid request. That makes it a drop-in contract data source for an agent tool-use loop, an MCP host, or a backend that needs crypto data on demand without onboarding to yet another vendor portal.
| Name | Type | Description |
|---|---|---|
chainrequired | string | EVM chain: ethereum, base, polygon, arbitrum, optimism, bsc, or avalanche. one of: ethereum | base | polygon | arbitrum | optimism | bsc | avalanche |
addressrequired | string | 0x-prefixed 40-hex contract address. |
selector | string | Optional 0x 4-byte function selector to decode (e.g. 0xa9059cbb). |
# 1. Probe with no auth → 402 envelope with PaymentRequirements curl -sS 'https://2s.io/api/crypto/contract?chain=ethereum&address=example&selector=example' # 2. Sign + retry with PAYMENT-SIGNATURE: curl -sS 'https://2s.io/api/crypto/contract?chain=ethereum&address=example&selector=example' \ -H 'PAYMENT-SIGNATURE: <base64-json-payload>' # Or use the canonical runner (handles probe → sign → retry): # EVM_PRIVATE_KEY=0x... node --env-file=.env.local \ # --experimental-strip-types scripts/x402-pay.ts \ # 'https://2s.io/api/crypto/contract?chain=ethereum&address=example&selector=example'
import { TwoS } from '@2sio/sdk'
const client = new TwoS({
privateKey: process.env.EVM_PRIVATE_KEY as `0x${string}`,
})
const result = await client.crypto.contract({
"chain": "ethereum",
"address": "example",
"selector": "example"
})
console.log('endpoint:', result.endpoint)
console.log('cost:', result.costUsd, 'USDC')
console.log('tx:', result.settlement?.txHash)
console.log('data:', result.data)import os
from twosio import TwoS
client = TwoS(private_key=os.environ["EVM_PRIVATE_KEY"])
result = client.crypto.contract(chain="ethereum", address="example", selector="example")
print("endpoint:", result.endpoint)
print("cost:", result.cost_usd, "USDC")
print("tx:", (result.settlement or {}).get("tx_hash"))
print("data:", result.data)// 1. Add @2sio/mcp to your MCP host config (Claude Desktop example below).
// EVM_PRIVATE_KEY funds x402 payments per call.
// claude_desktop_config.json
{
"mcpServers": {
"2sio": {
"command": "npx",
"args": ["-y", "@2sio/mcp"],
"env": { "EVM_PRIVATE_KEY": "0x..." }
}
}
}
// 2. Once the server is running, agents call this tool via standard MCP:
{
"jsonrpc": "2.0",
"id": 1,
"method": "tools/call",
"params": {
"name": "crypto.contract",
"arguments": {
"chain": "ethereum",
"address": "example",
"selector": "example"
}
}
}| Field | Type | Description |
|---|---|---|
ok | boolean | one of: true |
items | array | |
total | integer | Total matching rows upstream; null when unknown. |
source | object | |
meta | object |
{
"ok": true,
"items": [
{
"chain": "example",
"address": "example",
"verified": false,
"name": "example",
"compiler": "example",
"language": "example",
"isProxy": false,
"implementation": "example",
"functionCount": 1,
"functions": [
"example"
],
"events": [
"example"
],
"decoded": {
"selector": "example",
"signature": "example",
"source": "example"
}
}
],
"total": 1,
"source": {
"provider": "example",
"url": "example",
"license": "example"
},
"meta": {
"verified": false
}
}