Multicall Decoder

A CLI tool and library to decode multicall transaction data. It fetches ABIs from Etherscan and falls back to the 4byte directory for signature lookups.

Features

• Decodes multicall formats (Multicall2, Multicall3, tryAggregate, tryBlockAndAggregate)
• Supports multiple networks (Ethereum, Polygon, Arbitrum, Optimism, Base) - untested
• AI-powered explanations via Claude CLI

Installation

npm install
npm run build

For global installation:

npm install -g .

Usage

CLI Commands

Decode Multicall Transaction Data

# Basic usage
multicall-decoder decode <multicall-data># With Etherscan API key
multicall-decoder decode <multicall-data> --api-key YOUR_API_KEY
# With different network
multicall-decoder decode <multicall-data> --network polygon
# Verbose output
multicall-decoder decode <multicall-data> --verbose
# JSON output
multicall-decoder decode <multicall-data> --json
# Get AI explanation using Claude CLI
multicall-decoder decode <multicall-data> --explain
# Combine options
multicall-decoder decode <multicall-data> --verbose --explain --api-key YOUR_API_KEY

Decode Single Call

# Decode a single contract call
multicall-decoder decode-call <contract-address><call-data># With options
multicall-decoder decode-call <contract-address><call-data> --api-key YOUR_API_KEY --network mainnet
# With explanation
multicall-decoder decode-call <contract-address><call-data> --explain

Environment Variables

You can set the Etherscan API key as an environment variable:

export ETHERSCAN_API_KEY=your_api_key_here

CLI Options

Option	Description	Default
-k, --api-key <key>	Etherscan API key	ETHERSCAN_API_KEY env var
-n, --network <network>	Network to use	mainnet
-v, --verbose	Enable verbose output	false
-j, --json	Output as JSON	false
-e, --explain	Get AI explanation using Claude CLI	false

Examples

Example 1: Decode Multicall3 Transaction

multicall-decoder decode "0x82ad56cb00000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000002..."

Example 2: Get JSON Output

multicall-decoder decode <data> --json > output.json

Example 3: Get AI-Powered Explanation

# Requires Claude CLI to be installed and configured
multicall-decoder decode <data> --explain
# With verbose output to see contract names being fetched
multicall-decoder decode <data> --explain --verbose

The --explain flag uses the Claude CLI in pipe mode to provide:

• Plain-language explanation of what the transaction does
• Context about the contracts being called (fetched from Etherscan)
• Breakdown of arguments and their purpose
• Analysis of how calls work together

Development

# Install dependencies
npm install
# Run in development mode
npm run dev decode <data># Build the project
npm run build
# Run tests (if available)
npm test