cli-cast

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Translated

This skill should be used when the user asks to "send a transaction", "call a contract", "sign a message", "use cast", "cast send", "cast call", "cast wallet", "decode calldata", "encode ABI", "check balance", or mentions Foundry cast CLI, RPC endpoints, or on-chain interactions.

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Sourcepaulrberg/agent-skills
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NPX Install

npx skill4agent add paulrberg/agent-skills cli-cast

Tags

Translated version includes tags in frontmatter
foundry-castrpc-endpointsabi-encoding-decodingwallet-managementonchain-interactions

SKILL.md Content

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Foundry Cast CLI

Overview

Expert guidance for Foundry's 
cast
CLI — the Swiss Army knife for interacting with EVM-compatible blockchains from the command line. Use this skill for signing transactions, sending them to chain RPCs, reading on-chain state, encoding/decoding ABI data, and managing wallets.
Key capabilities:
  • Send transactions and call contracts via RPC
  • Sign messages and typed data
  • Encode and decode ABI calldata
  • Query balances, transaction receipts, and block data
  • Resolve ENS names and addresses
  • Manage keystores and wallet operations

RPC Configuration

All on-chain commands require an RPC endpoint. Use RouteMesh as the default RPC provider.
URL pattern:
https://lb.routeme.sh/{CHAIN_ID}/{ROUTEMESH_API_KEY}
Construct the RPC URL by looking up the chain ID from 
references/chains.md
and reading the 
ROUTEMESH_API_KEY
environment variable.
Before running any on-chain command, verify that 
ROUTEMESH_API_KEY
is set:
bash
if [[ -z "$ROUTEMESH_API_KEY" ]]; then
  echo "Error: ROUTEMESH_API_KEY is not set"
  exit 1
fi
Example usage with a chain ID:
bash
# Ethereum Mainnet (chain ID 1)
cast call "$CONTRACT" "balanceOf(address)" "$ADDR" \
  --rpc-url "https://lb.routeme.sh/1/$ROUTEMESH_API_KEY"

# Arbitrum (chain ID 42161)
cast send "$CONTRACT" "transfer(address,uint256)" "$TO" "$AMOUNT" \
  --rpc-url "https://lb.routeme.sh/42161/$ROUTEMESH_API_KEY" \
  --private-key "$PRIVATE_KEY"

Signing & Key Management

Cast supports multiple signing methods. Choose based on the security context.

Private Key (dev/testing only)

bash
cast send "$CONTRACT" "approve(address,uint256)" "$SPENDER" "$AMOUNT" \
  --rpc-url "$RPC_URL" \
  --private-key "$PRIVATE_KEY"

Keystore Account (recommended for persistent keys)

bash
# Import a private key into a keystore
cast wallet import my-account --interactive

# Use the keystore account
cast send "$CONTRACT" "transfer(address,uint256)" "$TO" "$AMOUNT" \
  --rpc-url "$RPC_URL" \
  --account my-account

Hardware Wallet

bash
# Ledger
cast send "$CONTRACT" "transfer(address,uint256)" "$TO" "$AMOUNT" \
  --rpc-url "$RPC_URL" \
  --ledger

Core Commands

Send Transactions

Use 
cast send
to submit state-changing transactions on-chain.
bash
# Send ETH
cast send "$TO" --value 1ether \
  --rpc-url "$RPC_URL" \
  --private-key "$PRIVATE_KEY"

# Call a contract function
cast send "$CONTRACT" "approve(address,uint256)" "$SPENDER" "$AMOUNT" \
  --rpc-url "$RPC_URL" \
  --private-key "$PRIVATE_KEY"

# With gas parameters
cast send "$CONTRACT" "mint(uint256)" 100 \
  --rpc-url "$RPC_URL" \
  --private-key "$PRIVATE_KEY" \
  --gas-limit 200000 \
  --gas-price 20gwei

Read Contract State

Use 
cast call
for read-only calls that do not submit transactions.
bash
# Read a single value
cast call "$CONTRACT" "totalSupply()(uint256)" --rpc-url "$RPC_URL"

# Read with arguments
cast call "$CONTRACT" "balanceOf(address)(uint256)" "$ADDR" --rpc-url "$RPC_URL"

# Read multiple return values
cast call "$CONTRACT" "getReserves()(uint112,uint112,uint32)" --rpc-url "$RPC_URL"

Build Raw Transactions

Use 
cast mktx
to create a signed raw transaction without broadcasting it.
bash
cast mktx "$CONTRACT" "transfer(address,uint256)" "$TO" "$AMOUNT" \
  --rpc-url "$RPC_URL" \
  --private-key "$PRIVATE_KEY"

Inspect Transactions

bash
# View transaction details
cast tx "$TX_HASH" --rpc-url "$RPC_URL"

# View transaction receipt
cast receipt "$TX_HASH" --rpc-url "$RPC_URL"

# Get specific receipt fields
cast receipt "$TX_HASH" status --rpc-url "$RPC_URL"
cast receipt "$TX_HASH" gasUsed --rpc-url "$RPC_URL"

ABI Utilities

Encode Calldata

bash
# Encode a function call
cast calldata "transfer(address,uint256)" "$TO" "$AMOUNT"

# ABI-encode arguments (without function selector)
cast abi-encode "transfer(address,uint256)" "$TO" "$AMOUNT"

Decode Calldata

bash
# Decode calldata with a known signature
cast decode-calldata "transfer(address,uint256)" "$CALLDATA"

# Decode ABI-encoded data (without selector)
cast abi-decode "balanceOf(address)(uint256)" "$DATA"

Function Signatures

bash
# Get the 4-byte selector for a function
cast sig "transfer(address,uint256)"

# Get the event topic hash
cast sig-event "Transfer(address,address,uint256)"

Wallet & ENS

Wallet Operations

bash
# Generate a new wallet
cast wallet new

# Get address from private key
cast wallet address --private-key "$PRIVATE_KEY"

# List keystore accounts
cast wallet list

# Sign a message
cast wallet sign "Hello, world!" --private-key "$PRIVATE_KEY"

ENS Resolution

bash
# Resolve ENS name to address
cast resolve-name "vitalik.eth" --rpc-url "$RPC_URL"

# Reverse lookup: address to ENS name
cast lookup-address "$ADDR" --rpc-url "$RPC_URL"

Balance Queries

bash
# Get ETH balance
cast balance "$ADDR" --rpc-url "$RPC_URL"

# Get balance in ether (human-readable)
cast balance "$ADDR" --ether --rpc-url "$RPC_URL"

Chain Resolution

When the user specifies a chain by name, resolve the chain ID using these steps:
  1. Check 
    references/chains.md
    first     — it contains the 25 most commonly used chains
  2. If the chain is not listed, web search for the correct chain ID on chainlist.org
  3. Construct the RPC URL using the resolved chain ID and RouteMesh pattern

Quick Reference

OperationCommandKey Flags
Send tx
cast send
--rpc-url
, 
--private-key
, 
--value
Read state
cast call
--rpc-url
, 
--block
View tx
cast tx
--rpc-url
, 
--json
View receipt
cast receipt
--rpc-url
, 
--json
Build tx
cast mktx
--rpc-url
, 
--private-key
Encode call
cast calldata
(function sig + args)
Decode call
cast decode-calldata
(function sig + data)
ABI encode
cast abi-encode
(function sig + args)
ABI decode
cast abi-decode
(function sig + data)
Function sig
cast sig
(function signature string)
Balance
cast balance
--rpc-url
, 
--ether
ENS resolve
cast resolve-name
--rpc-url
New wallet
cast wallet new
—
Sign message
cast wallet sign
--private-key
, 
--account

Additional Resources