Tool Guard

Tool Guard

Control which tools the agent can use and which need approval.

When to Use

• User wants to restrict the agent's capabilities for a sensitive task
• Working in production environments where certain operations are dangerous
• Reviewing unfamiliar code where unrestricted shell access is risky
• Pair programming where the user wants to approve every write/edit

Commands

Parse arguments to configure tool permissions:

• /tool-guard allow Read,Grep,Glob — only these tools, deny everything else
• /tool-guard deny Bash — block Bash, allow everything else
• /tool-guard gate Edit,Write — allow these tools but ask before each use
• /tool-guard gate Bash --pattern "rm|kill|drop|chmod" — gate Bash only for matching commands
• /tool-guard status — show current permissions
• /tool-guard reset — clear all restrictions

Permission Levels

Allow (default for all tools)

Tool can be used freely without notification.

Gate

Tool can be used, but the agent must explain what it's about to do and wait for user confirmation before proceeding.

Gate prompt format:

🔒 Tool Guard: requesting [tool-name]
   Action: [what the tool call will do, in plain English]
   Target: [file path, command, or URL]
   Why: [how this serves the current task]
   Proceed? (y/n)

Deny

Tool cannot be used. If the task requires it, explain to the user what you need and why, and ask them to either run the command themselves or adjust permissions.

Preset Profiles

For convenience, support named profiles:

readonly

• Allow: Read, Grep, Glob, Agent
• Gate: (none)
• Deny: Edit, Write, Bash, NotebookEdit

careful

• Allow: Read, Grep, Glob
• Gate: Edit, Write, Bash, Agent
• Deny: (none)

untrusted-repo

• Allow: Read, Grep, Glob
• Gate: Edit, Write
• Deny: Bash (no shell execution in untrusted code)

production

• Allow: Read, Grep, Glob
• Gate: Edit, Write, Bash (every shell command needs approval)
• Deny: (none, but all mutations gated)

Usage: /tool-guard profile readonly

Enforceable Team Profiles (hook-based)

The commands above are advisory — they ask the agent to self-restrict. For deterministic enforcement that a compromised skill or prompt injection cannot talk past, safe-agent ships a PreToolUse hook (hooks/tool-guard.sh) that reads a committed policy file and decides allow / ask / deny on every tool call, outside the agent's context.

Activate a preset by copying it to the project's policy file:

mkdir -p .safe-agent
cp profiles/careful.json .safe-agent/policy.json   # or readonly / untrusted-repo / production
git add .safe-agent/policy.json                     # commit it — the whole team gets the same enforcement

Wire the hook once via hooks/settings.example.json (PreToolUse, matcher ""). Because the policy lives in the repo, "what's enforced here" stops being per-developer tribal knowledge.

Policy format (profiles/*.json):

• tools.allow / tools.gate / tools.deny — tool names by tier.
• patterns.deny / patterns.gate — rules {tool?, match, reason} where match is an extended regex tested against the command (Bash), file path (Edit/Write/ Read), or URL (WebFetch). A rule with no tool applies to all tools.
• default — allow | deny | ask for tools not in any list.

Precedence (first match wins): tool in deny → deny; patterns.deny hit → deny; patterns.gate hit → ask (so "Bash allowed, but rm gated" works); tool in gate → ask; tool in allow → allow; else default. If no policy file exists, the hook defers to normal permission flow (no-op).

The behavioral commands and the hook compose: use a command for a one-off session restriction, commit a profile for durable team-wide enforcement.

Contextual Gating

Beyond static rules, apply contextual awareness:

1. Path-based gating: Gate writes to sensitive paths even if Write is allowed

   • .env*, *.key, *.pem, credentials* — always gate
   • **/config/production* — always gate
   • .claude/, .cursor/ — gate (agent config modification)

2. Command-based gating: When Bash is allowed, still gate commands matching:

   • Destructive patterns: rm -rf, git push --force, DROP TABLE
   • Network egress: curl -X POST, wget --post-data, scp
   • Privilege escalation: sudo, chmod 777, chown
   • Package publishing: npm publish, pip upload

3. Escalation: If the same tool is gated 3+ times in a row and the user approves each time, suggest: "You've approved [tool] 3 times — want me to allow it for the rest of this session?"

Status Report

When the user asks /tool-guard status:

## Tool Guard Status

Profile: careful (custom modifications)

| Tool    | Permission | Notes                          |
|---------|------------|--------------------------------|
| Read    | ✓ Allow    |                                |
| Grep    | ✓ Allow    |                                |
| Glob    | ✓ Allow    |                                |
| Edit    | 🔒 Gate    | Approved 2x this session       |
| Write   | 🔒 Gate    |                                |
| Bash    | 🔒 Gate    | + deny pattern: rm|kill|drop   |
| Agent   | ✓ Allow    |                                |

Gated calls this session: 4 (3 approved, 1 skipped)

Behavior

• The /tool-guard commands are advisory — they instruct the agent to self-restrict. The agent follows them because they are well-structured instructions, not because they are technically enforced. For deterministic enforcement that a compromised skill or prompt injection cannot bypass, commit a profile and wire the hooks/tool-guard.sh PreToolUse hook (see "Enforceable Team Profiles" above). The two layers compose.
• Always explain what you would have done with a denied tool, so the user can take that action themselves if needed.
• Never try to work around a denied tool by using a different tool for the same purpose (e.g., using Bash cat when Read is denied).
• Persist permissions for the duration of the session. They reset when the conversation ends.