From the README

# signet-eval

Deterministic policy enforcement for AI agent tool calls. Every action an agent proposes passes through user-defined rules before execution. No LLM in the authorization path. No prompt injection surface. 25ms end-to-end.

## Install

```bash
cargo install signet-eval
```

## Quick Start

**1. Hook into Claude Code** — add to `~/.claude/settings.json`:

```json
{
  "hooks": {
    "PreToolUse": [{
      "matcher": "",
      "hooks": [{"type": "command", "command": "signet-eval", "timeout": 2000}]
    }]
  }
}
```

**2. Done.** Every tool call now passes through policy evaluation. The default policy blocks destructive operations, protects its own configuration, and allows everything else.

**3. (Optional) Customize** — talk to Claude with the MCP server:

```bash
claude mcp add --scope user --transport stdio signet -- signet-eval serve
```

Then say: *"Add a $50 limit for amazon orders"* or *"Block all rm commands"*.

## Default Policy

Self-protection rules are **locked**