Ethereum Transaction Builder

io.github.nirholasPublished by GitHub account nirholasv1.0.0Updated Oct 24, 2026

Build and sign Ethereum transactions - EIP-1559, gas estimation, RLP, ERC-20 transfers

The publisher's own server: WAI Quantum job service

VerifiedSTDIODesktop onlyFinanceDeveloper Tools

Overview

AI-generated overview

Local MCP server that lets an assistant build, sign, decode and analyze Ethereum transactions, including EIP-1559 and ERC-20 transfers.

What you can do
Build and sign legacy or EIP-1559 transactions, including one-step build-and-sign and ERC-20 transfer calldata encoding, plus arbitrary function call encoding and calldata decoding. Decode signed raw or unsigned transactions and recover the signer address. Estimate gas cost in ETH, validate transaction fields, compare two transactions and calculate maximum cost. Convert between wei, gwei and ether, and RLP-serialize transactions. Read bundled reference resources on transaction types, gas estimation, chain IDs and EIP-1559, and follow guided prompts for transfers, decoding and gas optimization.
When to use it
Useful when you want an assistant to prepare or inspect Ethereum transactions offline: drafting a transfer, checking gas and fees, decoding a raw transaction, or explaining EIP-1559 fields before you broadcast anything yourself.
Requirements
Runs locally as a stdio process, installed from PyPI (pip install transaction-mcp-server) or run with uvx; a Python environment is needed. No accounts, API keys or environment variables are declared. Signing is described as offline, so no network access is required for the tools themselves.
Before you install
Signing tools take a private key as an input parameter; the README says keys are never logged or persisted, but you are handing a signing secret to a local process, so prefer test keys. Signed raw transactions are not broadcast by the server and must be sent separately. The README labels the project as for educational and development purposes only.

Installation

In SourceWeft

  1. Open Ethereum Transaction Builder in the dashboard and add it to a workspace.
  2. Enable the server for the chats that should use its tools.

Desktop only via STDIO. STDIO servers start a local process, so they need the SourceWeft desktop host.

Other MCP clients

Follow the launch instructions in the repository.

README

Transaction MCP Server

[PyPI] [MCP Registry]

An MCP (Model Context Protocol) server providing comprehensive Ethereum transaction capabilities including building, signing, decoding, and analysis for both legacy and EIP-1559 transactions.

Features

Tools (15 total)

Transaction Building & Signing
  • build_transaction - Build an unsigned transaction
  • sign_transaction - Sign a transaction with a private key
  • build_and_sign_transaction - Build and sign in one step
Transaction Decoding
  • decode_raw_transaction - Decode a signed raw transaction
  • decode_unsigned_transaction - Decode an unsigned transaction
  • recover_transaction_signer - Recover signer from signed transaction
Transaction Analysis
  • estimate_transaction_cost - Estimate gas cost in ETH
  • validate_transaction - Validate transaction fields
  • compare_transactions - Compare two transactions
Gas Utilities
  • convert_gas_units - Convert between wei, gwei, ether
  • calculate_max_cost - Calculate maximum transaction cost
Data Encoding
  • encode_transfer - Encode ERC-20 transfer calldata
  • encode_function_call - Encode arbitrary function call
  • decode_calldata - Decode transaction input data
Serialization
  • serialize_transaction - RLP encode a transaction

Resources (4 total)

  • transaction-types - Documentation on transaction types (Legacy, EIP-2930, EIP-1559)
  • gas-estimation - Guide to gas estimation and optimization
  • chain-ids - Chain ID reference for all networks
  • eip-1559 - EIP-1559 fee mechanism explained

Prompts (4 total)

  • build_transfer_workflow - Guide through building an ETH transfer
  • token_transfer_workflow - Guide through ERC-20 token transfers
  • decode_transaction_workflow - Help decode and analyze transactions
  • gas_optimization_workflow - Optimize transaction gas costs

Installation

bash
pip install transaction-mcp-server

Or install from source:

bash
cd transaction-mcp-serverpip install -e .

Usage

Run the server

bash
transaction-mcp-server

Configure in Claude Desktop

json
{  "mcpServers": {    "transaction": {      "command": "transaction-mcp-server"    }  }}

Tool Examples

Sign a Simple Transfer

python
# Input{    "to": "0x742d35Cc6634C0532925a3b844Bc9e7595f5b4E2",    "value": "1000000000000000000",  # 1 ETH in wei    "nonce": 0,    "chain_id": 1,    "max_fee_per_gas": "30000000000",    "max_priority_fee_per_gas": "2000000000",    "private_key": "0x..."}
# Output{    "raw_transaction": "0x02f8...",    "transaction_hash": "0x...",    "from": "0xABC...",    "to": "0x742...",    "value_eth": "1.0",    "type": "EIP-1559"}

Decode a Transaction

python
# Input{    "raw_transaction": "0x02f8..."}
# Output{    "type": "EIP-1559 (Type 2)",    "chain_id": 1,    "nonce": 0,    "to": "0x742...",    "value_wei": "1000000000000000000",    "value_eth": "1.0",    "max_fee_per_gas_gwei": "30.0",    "max_priority_fee_per_gas_gwei": "2.0"}

Transaction Types

TypeEIPDescription
Legacy (0)-Original Ethereum transactions
Access List (1)EIP-2930With access list for gas savings
Dynamic Fee (2)EIP-1559Base fee + priority fee model

Security Notes

  1. Private keys are NEVER logged or persisted
  2. Transactions are signed OFFLINE - no network connection
  3. Raw transactions must be broadcast separately
  4. For educational and development purposes only

Chain IDs

ChainID
Ethereum Mainnet1
Goerli5
Sepolia11155111
Polygon137
Arbitrum One42161
Optimism10
Base8453

License

MIT

Source: transaction-mcp-server/README.md at commit dabb599

Tools

0
SourceWeft has not started this package in its sandbox yet, so its tools are not known.

Version history

1
  1. v1.0.0LatestSep 16, 2026

Score

40% of the applicable checks met

How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.

  • Reached in the last 30 days25 pts

    Keep the endpoint answering the MCP handshake; SourceWeft probes it every 30 days.

  • Auth declared10 pts

    Declare the credential headers in the registry entry, or keep the endpoint answering the probe so its auth can be classified.

  • Tools listed15 pts

    Answer tools/list without a credential, or ship a package that starts in a sandbox without one.

  • DescriptionRequired15 pts
  • Logo10 pts
  • Documentation15 pts
  • License10 pts

    Declare a license in the repository or the registry entry.

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