Ship production-ready notifications with Gemini CLI

Overview

How Gemini CLI and Courier fit together

Gemini CLI is Google's open-source coding agent for the terminal. With the Courier skill installed, it builds your notification system in your codebase, templates with fallback routing, journeys, preferences, and an in-app inbox, following Courier's patterns for each channel. Courier then makes sure those messages reach people: it picks the channel, falls back when one fails, respects the user's preferences, and shows you what happened.

The skill does the building. Add the hosted MCP server when you want to test against your account from the editor. Gemini CLI takes the server in settings.json, user-wide or per project; httpUrl selects the streamable HTTP transport the Courier server speaks.

You need a Courier account. The skill needs nothing else; the MCP server needs a test-environment API key, which is separate from production.

What you can build

What you get with Gemini CLI + Courier

Agent skills

Patterns it reads before it writes

One install. Gemini CLI opens the skill's router, loads the one or two guides a task needs, and writes sends that follow the rules for that channel: OTP expiry, fallback order, idempotency keys, rate limits.

Templates

Templates with fallback routing

Ask for a password-reset flow with SMS first and email fallback and it builds the template and the routing, in your repo, from one prompt.

Courier Inbox

An in-app inbox in your app

Scaffold the Inbox component into a React or Next.js app and issue the user JWT server-side. The skill's inbox guides carry the auth and rendering patterns.

Journeys

Journeys with delays and branches

Build a multi-step onboarding journey with a two-day delay between steps, then publish it and run it for a test user.

Preferences

Preference topics users can opt out of

Create a preference section and topic, publish them, and wire your templates to respect the opt-out.

MCP

Test and prototype over MCP

Add the hosted server and Gemini CLI can create a template in your test workspace, send you a test, and pull the delivery events, so you see the message reach someone before you ship. 144 tools, one config block to add.

Use cases

What to build in your first session

→Add password-reset notifications to this app with Courier: SMS first, email fallback

→Add Courier Inbox to this Next.js app with a server-issued JWT

→Build a three-step onboarding journey with a two-day delay between steps

→Add a Product updates preference topic users can opt out of, and make onboarding respect it

Setup

Set up Gemini CLI with Courier

Two steps to build. Two more if you want to test against your account from the editor.

Install the Courier skill

Works in any tool that reads a skills directory. Discovery comes from the SKILL.md frontmatter; there is nothing else to configure.

npx skills add trycourier/courier-skills

Kick off a build

Gemini CLI reads the skill's router, loads the guides for the task, and writes the code and templates in your repo.

› Add password-reset notifications to this app with Courier:
  SMS first, email fallback

Add the MCP server to test and prototype

Optional. Needs your test-environment API key from app.courier.com/settings/api-keys. To confirm the key works, ask it to list your notification templates; a wrong key returns a 403. Add this to ~/.gemini/settings.json for every project, or .gemini/settings.json for one. Paste the key itself; Gemini CLI does not expand environment variables inside headers.

{
  "mcpServers": {
    "courier": {
      "httpUrl": "https://mcp.courier.com",
      "headers": { "api_key": "YOUR_COURIER_API_KEY" }
    }
  }
}

Send yourself a test

Over MCP, Gemini CLI publishes the template to your test workspace, sends to your test user, and reads back the delivery events.

› Publish the password-reset template and send me a test

FAQ

Frequently asked questions

What does the Courier skill add?

A routing file plus about 40 reference guides covering seven channels, transactional and growth patterns, routing, reliability, and Inbox. Gemini CLI reads the router first and loads only the one or two guides a task needs. It is plain Markdown on the open agent-skills convention, so the same skill works in every tool that reads a SKILL.md.

Do I need the MCP server?

Not to build. The skill is enough for Gemini CLI to write templates, routing, journeys, and Inbox code in your repo. Add the MCP server when you want to test and prototype against your Courier account from the editor: publish to your test workspace, send yourself a test, read the delivery events.

What can Gemini CLI do through the Courier MCP server?

The hosted server exposes 144 tools covering the full Courier API: create and publish templates, define routing strategies, build and run journeys, set up preference topics and brands, manage users and lists, send test messages, and read message logs. It authenticates with your API key passed as a header; nothing runs locally.

Why httpUrl and not url?

In Gemini CLI, httpUrl selects the streamable HTTP transport, which is what the Courier server speaks. The url field selects SSE, a different transport.

Is it safe to let it work against my account?

Use the test-environment API key. Test and production keys are separate, so templates, journeys, and test sends stay in the test environment and never reach real users. Switch to the production key when you ship.

How is this different from the Claude and ChatGPT integrations?

Those cover AI assistants: Claude the model inside Courier (AI agent node, AI Translation) and connecting a ChatGPT agent to Courier. This page is Gemini CLI, the coding tool, building your notification system in your codebase with the Courier skill.