# Ethereum Address Validator

Validates Ethereum addresses, private keys and EIP-55 checksums inside your agent session. Handy when you need to confirm an address or work out a function selector.

- MCP server · `type=mcp` · Claude Code, Codex, Cursor, GitHub Copilot, Windsurf (Devin Desktop), Cline, Zed, Gemini CLI · ★ 28
- Author: nirholas
- License: not stated · policy=link-only · description only; the file stays with the author
- Source: https://github.com/nirholas/ethereum-wallet-toolkit/tree/HEAD/validation-mcp-server
- Updated: 2026-10-19
- HTML: https://affpapa.org/en/nevibecode/mcp/ethereum-address-validator

## What it does

The server hands your agent 15 tools. They cover address validation with EIP-55 checksum verification, private key range checks, conversion of any address to checksummed form, address derivation from a private or public key, ECDSA signature component checks, address comparison and batch validation of a list. There is also `keccak256_hash`, encoding and decoding of 4-byte function selectors, ENS name format validation and contract storage slot calculation.

Alongside the tools come resources: the EIP-55 specification, secp256k1 curve parameters, a database of common function selectors, known address patterns and weak key information. Ready-made prompts cover an address validation workflow, a key security audit, data encoding help and contract interaction preparation.

Private keys are never logged or persisted, and sensitive operations wipe memory afterwards. ENS name validation runs offline, with no network call. The server launches through `uvx`, so `uv` has to be on your `PATH` — otherwise the start command fails.

## Requirements
- Needs: Python and uv (commands run via uvx)

## Install

### Claude Code (native platform)

**Platform CLI**
```bash
claude mcp add validation-mcp-server -- uvx validation-mcp-server
```
uvx runs the command named after the package; if the README names another one, use uvx --from validation-mcp-server <command>

### Codex

**Platform CLI**
```bash
codex mcp add validation-mcp-server -- uvx validation-mcp-server
```
uvx runs the command named after the package; if the README names another one, use uvx --from validation-mcp-server <command>

### Cursor

**Config file**
File `.cursor/mcp.json`:
```json
{
    "mcpServers": {
        "validation-mcp-server": {
            "command": "uvx",
            "args": [
                "validation-mcp-server"
            ]
        }
    }
}
```
uvx runs the command named after the package; if the README names another one, use uvx --from validation-mcp-server <command>

### GitHub Copilot

**Config file**
File `.vscode/mcp.json`:
```json
{
    "servers": {
        "validation-mcp-server": {
            "type": "stdio",
            "command": "uvx",
            "args": [
                "validation-mcp-server"
            ]
        }
    }
}
```
uvx runs the command named after the package; if the README names another one, use uvx --from validation-mcp-server <command>

### Gemini CLI

**Platform CLI**
```bash
gemini mcp add validation-mcp-server uvx validation-mcp-server
```
uvx runs the command named after the package; if the README names another one, use uvx --from validation-mcp-server <command>

## When to use it
- check an address and its EIP-55 checksum
- confirm a private key sits inside the valid range
- convert an address to checksummed form before sending it
- turn a function signature into its 4-byte selector
- validate a whole list of addresses in one go

## Example prompts
- Validate `0x5aaeb6053f3e94c9b9a09f33669435e7ef1beaed` and tell me if the checksum is right
- Encode the selector for `transfer(address,uint256)`
- Derive the address from private key `0x4c0883a69102937d6231471b5dbb6204fe5129617082792ae468d01a3f362318`

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From the same set: [nirholas/ethereum-wallet-toolkit](https://affpapa.org/en/nevibecode/by/nirholas/ethereum-wallet-toolkit.md) — 2 cards

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