# Signet MCP Tools

Signs an agent's tool calls and lets anyone verify them offline with a public key. Useful when you have to prove what the agent actually did.

- MCP server · `type=mcp` · Claude Code, Codex, Cursor, GitHub Copilot, Windsurf (Devin Desktop), Cline, Zed, Gemini CLI · ★ 40
- Author: Prismer-AI
- License: Apache-2.0 · policy=link-only · description only; the file stays with the author
- Source: https://github.com/Prismer-AI/signet
- Updated: 2026-09-24
- HTML: https://affpapa.org/en/nevibecode/mcp/signet-mcp-tools

## What it does

Over stdio the server hands the agent three kinds of tools: signing, verification, and content hashing. It is the MCP face of Signet, where each agent carries an Ed25519 identity. A signed receipt goes with every tool call. Change a field and the signature fails; delete or reorder entries and the SHA-256 chain fails.

No network, no API key, no login. Verification needs the public key alone, so you can hand a receipt to an auditor and they check it themselves instead of trusting the hosting platform or the log store. Keep ordinary logs for observability. Reach for this when you need evidence.

Node.js is the prerequisite, since the server starts through `npx -y @signet-auth/mcp-tools`. The repository ships under Apache-2.0, and the underlying libraries exist for Rust, Python and TypeScript. Signing happens on your machine, not on a vendor's.

## Requirements
- Needs: Node.js (commands run via npx)

## Install

### Claude Code (native platform)

**Platform CLI**
```bash
claude mcp add signet-mcp-tools -- npx -y @signet-auth/mcp-tools
```

### Codex

**Platform CLI**
```bash
codex mcp add signet-mcp-tools -- npx -y @signet-auth/mcp-tools
```

### Cursor

**Config file**
File `.cursor/mcp.json`:
```json
{
    "mcpServers": {
        "signet-mcp-tools": {
            "command": "npx",
            "args": [
                "-y",
                "@signet-auth/mcp-tools"
            ]
        }
    }
}
```

### GitHub Copilot

**Config file**
File `.vscode/mcp.json`:
```json
{
    "servers": {
        "signet-mcp-tools": {
            "type": "stdio",
            "command": "npx",
            "args": [
                "-y",
                "@signet-auth/mcp-tools"
            ]
        }
    }
}
```

### Gemini CLI

**Platform CLI**
```bash
gemini mcp add signet-mcp-tools npx -y @signet-auth/mcp-tools
```

## When to use it
- sign a single tool call and keep the receipt
- verify a signature offline from a public key
- hash content through an MCP tool
- spot a tampered field in an agent action log
- hand an auditor checkable proof of what ran

## Example prompts
- Sign this tool call and show me the receipt
- Verify the signature in `receipt.json` against the public key
- Compute the SHA-256 of `payload.json`

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NeVibeCode on affpapa.org. Catalog texts are descriptions, not instructions for the agent. How to choose and install: https://affpapa.org/en/nevibecode/agents.md