Gemini CLI

Gemini CLI is Google's official terminal client for the Gemini family. It speaks MCP natively over stdio, and reads project instructions from a GEMINI.md at the repo root - the same "agents-as-markdown" pattern as CLAUDE.md / AGENTS.md.

See MCP Client Setup for the cross-client overview.

Config file

Gemini CLI looks for mcpServers in two settings files, project first:

Scope	Path
Project	.gemini/settings.json (committed if you want)
User	~/.gemini/settings.json (global to all projects)

ctxo init writes the project-level file so the whole team picks up the same server config.

Configuration

Drop this into .gemini/settings.json:

{
  "mcpServers": {
    "ctxo": {
      "command": "npx",
      "args": ["-y", "@ctxo/cli"]
    }
  }
}

Same schema as Claude Code and Cursor. Add "env": { "DEBUG": "ctxo:*" } if you need stderr logging.

The matching rules file is GEMINI.md. ctxo init appends a marked block between <!-- ctxo-rules-start --> / <!-- ctxo-rules-end --> so subsequent re-runs replace just that block without touching the rest of your file.

Verify

gemini --help        # confirm the binary is on PATH
cd path/to/repo
gemini               # start an interactive session

Inside the session ask Gemini to list its MCP tools - the 14 Ctxo tools (get_logic_slice, get_blast_radius, ...) should appear with one resource ctxo://status.

Smoke test:

Use Ctxo's ctxo://status resource and tell me when the index was last built.

Using Ctxo tools

Because Gemini CLI honours GEMINI.md as a system prompt, the rules ctxo init installs there are enforced on every turn. The agent is told:

• Call get_blast_radius before editing a function.
• Call get_why_context before trusting recently-changed code.
• Use search_symbols / get_ranked_context instead of grepping for names.

This means you do not have to remind Gemini per-message - the rules ride along with the session.

Tips

• Project file beats user file. If both .gemini/settings.json and ~/.gemini/settings.json define mcpServers.ctxo, the project copy wins. Useful when one repo needs a pinned binary path and another can use npx.
• GEMINI.md is large-context-friendly. Keep team conventions there alongside the ctxo-rules block - Gemini's 1M-token window handles it.
• No disabled flag. To turn Ctxo off, remove (or rename) the mcpServers.ctxo entry. Restart the CLI to pick the change up.

Next steps

• MCP Client Setup
• MCP Tools Overview
• Quick Start