Gemini CLI

This guide shows how to integrate Gemini CLI with Maybe Don’t using hooks.

Prerequisites

Maybe Don’t gateway running in http or sse mode (see Get Started)
Gemini CLI installed
jq and curl on PATH
MAYBE_DONT_URL environment variable set (e.g., http://localhost:8080)

Install the Hook

Export the hook script into your project’s .gemini/hooks/ directory:

mkdir -p .gemini/hooks
maybe-dont hooks export --agent gemini-cli > $GEMINI_PROJECT_DIR/.gemini/hooks/maybe-dont-hook.sh
chmod +x $GEMINI_PROJECT_DIR/.gemini/hooks/maybe-dont-hook.sh

Configure Gemini CLI

Export the config snippet:

maybe-dont hooks export --agent gemini-cli --config

This outputs a JSON snippet to merge into your Gemini CLI settings.json. Update the command path to where you placed the hook script:

{
  "hooks": {
    "BeforeTool": [
      {
        "type": "command",
        "command": "$GEMINI_PROJECT_DIR/.gemini/hooks/maybe-dont-hook.sh"
      }
    ],
    "AfterTool": [
      {
        "type": "command",
        "command": "$GEMINI_PROJECT_DIR/.gemini/hooks/maybe-dont-hook.sh"
      }
    ]
  }
}

Set the gateway URL before starting Gemini CLI:

export MAYBE_DONT_URL="http://localhost:8080"

Supported Events

Event	Phase	Description
`BeforeTool`	Pre-tool	Fires before Gemini CLI executes a tool. The hook can block the tool call.
`AfterTool`	Post-tool	Fires after tool execution. Observability only — results are logged but cannot be blocked or modified.

Verify It Works

Start Gemini CLI and trigger a tool call. Check the gateway’s audit log for entries — you should see an intercept record for the tool call.

gemini

The hook is silent on allow. On deny, you’ll see stderr output like:

[maybe-dont] WARNING (AfterTool): Policy violation detected for '<tool_name>' — <reason>

Filtering

Gemini CLI hooks support a matcher field that uses regex for tool events (BeforeTool, AfterTool) and exact strings for lifecycle events. Use "*" or omit the matcher to match all tools.

{
  "BeforeTool": [
    {
      "matcher": "write_file|replace",
      "hooks": [
        {
          "type": "command",
          "command": "$GEMINI_PROJECT_DIR/.gemini/hooks/maybe-dont-hook.sh"
        }
      ]
    }
  ]
}

To change what triggers the hook, update the matcher field in your Gemini CLI settings.json. See the Gemini CLI hooks documentation for details.

Agent-Specific Notes

Gemini CLI hooks apply to the CLI tool only — not the Gemini Code Assist IDE extension.
$GEMINI_PROJECT_DIR resolves to the project root at runtime, ensuring the hook works regardless of the agent’s working directory.
Gemini CLI passes tool details as JSON on stdin to the hook script.

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