MCP Servers vs. Extensions in Gemini CLI

If you've been using Gemini CLI, you've probably noticed there are two main ways to extend its capabilities. You can add MCP servers directly to your configuration, or you can install extensions. Both approaches let you add new tools and features, but they serve different purposes.

Choosing between them isn't always obvious. Should you configure that database server directly in your settings, or package it as an extension? The answer depends on what you're trying to accomplish and who else might benefit from your setup.

Let's break down the differences and help you figure out which approach fits your needs.

What Are MCP Servers?

MCP servers are the building blocks of Gemini CLI's extensibility. They're standalone programs that expose tools, resources, and prompts to the CLI. Think of them as plugins that give Gemini new capabilities.

When you add an MCP server, you configure it in your settings.json file. You specify the command to run the server, any environment variables it needs, and which workspace or user profile should have access to it. The CLI starts these servers when you launch a session and communicates with them throughout your conversation.

For example, you might add a filesystem server that lets Gemini read and write files. Or a database server that can run SQL queries. Or a browser automation server that can interact with web pages. Each server brings its own set of tools to the table.

The key thing about MCP servers is that they're configured per user or per workspace. Your setup is yours. Your credentials, your paths, your preferences. This makes them perfect for personal integrations and private infrastructure.

What Are Extensions?

Extensions take a different approach. They're packaged bundles that can include MCP servers, but they also bring along custom commands, context files, and tool restrictions. When you install an extension, you're getting a complete toolkit designed for a specific purpose.

Think of extensions as curated experiences. Someone has already figured out which MCP servers work well together, what commands are useful, what context information helps, and what safety guardrails make sense. They've packaged all of that into something you can install with a single command.

Installing an extension is straightforward. You run gemini extensions install with a GitHub URL or local path, and Gemini CLI pulls in everything the extension provides. Note that you'll need git installed on your machine for GitHub installations. The extension handles the configuration structure, though you might still need to provide credentials or API keys if the extension includes MCP servers that require them. Restart your CLI session after installation to see the changes take effect.

Extensions also come with management tools. You can enable or disable them globally or per workspace. You can update them when new versions come out. You can uninstall them cleanly. They're designed to be shareable and discoverable, which makes them great for teams and communities.

When to Use MCP Servers

There are several scenarios where configuring MCP servers directly makes more sense than using extensions.

If you're working with personal or private infrastructure, MCP servers are the way to go. Your company's internal APIs, your personal task tracker, your specific database instances. These all need credentials and configuration that are unique to you. Putting them in your settings.json keeps them private and gives you full control over how they're set up.

Highly configurable setups also benefit from direct MCP server configuration. Maybe you need different database connections for different projects. Or different API keys for different clients. Or custom environment variables that change based on context. The flexibility of per-workspace MCP server configuration handles these cases well.

Development and testing is another clear use case. When you're building your own MCP server, you want to iterate quickly. Configure it directly in your settings, make changes, restart the CLI, and test. No need to package it as an extension until you're ready to share it with others.

Single-purpose integrations work well as direct MCP servers too. If you just need filesystem access, add the filesystem server. If you just need to run shell commands, add that server. Sometimes you don't need the overhead of an extension when a simple server configuration does the job.

Here's a concrete example. Let's say you need to query your company's production database for debugging. You'd configure the database MCP server in your settings.json with your credentials and connection string. That's it. Quick, private, and exactly what you need.

When to Use Extensions

Extensions shine in different scenarios. They're all about packaging and sharing opinionated workflows.

If you're building distributable toolkits for your team, extensions are perfect. A security scanning extension that everyone on the team should use. A code generation extension for your framework. A deployment extension with your company's best practices baked in. These are workflows you want to standardize and share.

Opinionated workflows benefit from extensions because they can bundle everything needed. Consider a "deploy to AWS" extension. It might include an AWS MCP server, custom commands like /deploy:staging and /deploy:production, context documentation about your deployment process, and tool restrictions that prevent dangerous operations. All of that packaged together creates a smooth experience.

Team standardization is a huge win with extensions. New team members can install your extension and immediately have access to all the tools, commands, and documentation they need. No lengthy setup guides. No copying configuration files around. Just install and go.

Community sharing is where extensions really stand out. You can publish an extension to GitHub and let anyone install it. Open source projects can provide extensions that give contributors the right tools and context. Educational content can be packaged as extensions that teach frameworks or best practices.

Think about a "web development" extension as an example. It could include a browser automation MCP server, a file watcher server, and a git server. It could provide custom commands like /preview:browser and /test:e2e. It could include context about web development best practices. And it could restrict certain dangerous shell commands for safety. That's a complete toolkit that others can benefit from.

Real-World Scenarios

Let's look at a few side-by-side comparisons to make the decision process clearer.

Database access is a good example. If you're connecting to your local Postgres database for personal development, configure the database MCP server directly with your credentials. But if you're building a "database migration" toolkit with migration commands, rollback procedures, and safety checks that your whole team should use, package it as an extension.

Security scanning is another one. If you're experimenting with a security analysis tool and configuring it with your preferences, use an MCP server. But if you've settled on a security workflow with specific tools, custom analysis commands, and documentation about security best practices that you want to share, make it an extension.

Deployment workflows follow the same pattern. Your personal AWS credentials and one-off deployment scripts? MCP server configuration. A complete deployment system with staging and production commands, rollback procedures, environment checks, and team documentation? Extension.

The pattern here is clear. Personal configuration and credentials go in MCP servers. Shareable workflows and curated experiences go in extensions.

Conclusion

The choice between MCP servers and extensions comes down to scope and shareability. MCP servers are for personal setups, private infrastructure, and flexible configurations. Extensions are for packaged workflows, team standardization, and community sharing.

Most people will use both. You'll have some MCP servers configured directly for your personal tools and credentials. And you'll have extensions installed that provide team workflows and shared capabilities. That's exactly how the system is designed to work.

Don't overthink it. Start with direct MCP server configuration when you need something quick and personal. Graduate to extensions when you have something worth sharing. And remember, you can always convert a working MCP server setup into an extension later when you're ready to package it for others.

The best way to learn is to try both approaches and see what feels right for your use cases. The Gemini CLI team has made both paths straightforward, so experiment and find what works for you.