crypto.contract

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.

price

$0.0018 USDC per call

method

GET/api/crypto/contract

payment

x402 v2 · USDC on Base (EIP-3009) or Solana (SPL transfer)

auth

None. Sign the payment, retry with PAYMENT-SIGNATURE.

tier

Tier 0 — no paid upstream

Parameters

Name	Type	Description
`chain`required	string	EVM chain: ethereum, base, polygon, arbitrum, optimism, bsc, or avalanche. one of: ethereum \| base \| polygon \| arbitrum \| optimism \| bsc \| avalanche
`address`required	string	0x-prefixed 40-hex contract address.
`selector`	string	Optional 0x 4-byte function selector to decode (e.g. 0xa9059cbb).

Code samples

cURLbash

# 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'

TypeScript / Node — @2sio/sdktypescript

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)

Python — 2siopython

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)

MCP — Claude Desktop / AgentKit / any MCP hostjson

// 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"
    }
  }
}

Response

Field	Type	Description
`ok`	boolean	one of: true
`items`	array
`total`	integer	Total matching rows upstream; null when unknown.
`source`	object
`meta`	object

Example response datajson

{
  "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
  }
}

Discovery

/api/directory — full catalog of every endpoint
/openapi.json — OpenAPI 3.1 spec (per-op x-payment-info, x402Payment security)
/.well-known/x402 — machine-readable service descriptor for x402-aware crawlers
/.well-known/mcp/server-card.json — MCP SEP-1649 server card
/llms.txt — plain-text manifest for LLM ingestion

2s.io is x402-native. Every call is paid per-request from a USDC-funded EVM wallet on Base — no signup, no API keys, no monthly fees. Source code: github.com/2s-io/sdk.