cher": "Write|Edit",
      "hooks": [{
        "type": "command",
        "command": "jq -r '.tool_response.filePath // .tool_input.file_path' | xargs prettier --write 2>/dev/null || true"
      }]
    }]
  }
}
```

### Adding Permissions

User: "Allow npm commands without prompting"

1. **Read**: Existing permissions
2. **Merge**: Add `Bash(npm:*)` to allow array
3. **Result**: Combined with existing allows

### Environment Variables

User: "Set DEBUG=true"

1. **Decide**: User settings (global) or project settings?
2. **Read**: Target file
3. **Merge**: Add to env object
```json
{ "env": { "DEBUG": "true" } }
```

## Common Mistakes to Avoid

1. **Replacing instead of merging** - Always preserve existing settings
2. **Wrong file** - Ask user if scope is unclear
3. **Invalid JSON** - Validate syntax after changes
4. **Forgetting to read first** - Always read before write

## Troubleshooting Hooks

If a hook isn't running:
1. **Check the settings file** - Read ~/.claude/settings.json or .claude/settings.json
2. **Verify JSON syntax** - Invalid JSON silently fails
3. **Check the matcher** - Does it match the tool name? (e.g., "Bash", "Write", "Edit")
4. **Check hook type** - Is it "command", "prompt", or "agent"?
5. **Test the command** - Run the hook command manually to see if it works
6. **Use --debug** - Run `claude --debug` to see hook execution logs