MCP for All: Solving the Auth Problem

‍Executive Summary:

Today, Civic unveiled a new library, @civic/auth-mcp, offering the fastest way to add authorization to MCP servers with simplified OAuth 2.0 integration solutions. Authentication is critical for security and multi-user access control.

Key Takeaways: 

• Authentication solutions must address both server-side security and diverse client capabilities, from desktop applications to backend services with varying token acquisition methods.
• OAuth 2.0 integration in MCP specifications is complex and lacks tooling, making implementation challenging for developers without specialized libraries.
• Devs can access our technical guide for easy implementation.

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Understanding MCP Servers and Their Growing Importance

Let's start with the basics. What exactly are MCP servers, and why are they gaining traction now?

MCP servers, or Model Context Protocol servers, standardize the way that LLMs interact with the world. Specifically, they standardize the way that LLMs can execute tools that let them change things in the world—whether that's accessing databases, making API calls, or triggering automated workflows. This takes LLMs out of the space of being just a helpful chatbot or a way to generate texts and images, to actually performing tasks that are currently performed by humans.

The significance of this shift cannot be overstated—we're moving from AI as a conversational interface to AI as an active participant in real-world workflows and processes.

The Shift from Local Tools to Accessible Services: Why Authentication Becomes Paramount

So, why is authentication particularly important in this context of MCP servers?

Well, MCP servers have sort of gone through two phases, or rather, they've finished phase one and are starting phase two. In phase one, they are installed on a local machine, usually of an engineer or software developer—at the very least, someone technical enough to install tools locally. Think of this as the "proof of concept" stage where individual developers could experiment with AI agent capabilities in a controlled, single-user environment.

Okay, that makes sense. In this initial phase, security might not be the biggest concern since it's mostly for local, individual use. But what changes in phase two that makes authentication so crucial?

That local setup limits their flexibility and use and puts them out of reach of a lot of people. That's why they're starting to move into phase two. Phase two has MCP servers either hosted remotely, and then you can connect to them via the internet like any other API, software as a service, or website. This shift democratizes access to AI agent capabilities, allowing businesses and non-technical users to leverage these tools without complex local installations.

I see. So, as MCP servers become more accessible over the internet, the need for robust authentication becomes critical. Can you elaborate on the specific security risks that arise in this second phase?

Yes. Inherent in the second phase is that MCP servers are shared by multiple users. They need access control, the same as any resource on the Web. Without proper authentication, you're essentially opening powerful AI capabilities to anyone on the internet—which creates both security vulnerabilities and potential abuse scenarios.

That's right. And as you mentioned, the MCP spec and Anthropic, who wrote it, have anticipated this and have incorporated support into the spec.

Yes, they've incorporated OAuth 2.0 support.

Can you explain a bit more about how OAuth 2.0 addresses the authentication challenges in this context?

Essentially, what you're doing here is saying that an MCP server requires some permissions, and it is up to the client—the MCP client—to obtain those permissions. Once you obtain those permissions, you're able to present what's called an access token to the MCP server, and the MCP server will now know who is calling it. This creates a secure handshake where the server can verify identity, apply appropriate access controls, and track usage patterns—all critical for production deployments.

Exactly. OAuth 2.0 provides a standardized way for MCP servers to verify the identity of the client and ensure they have the necessary permissions. This is crucial for security.

The "Snag": Navigating the Complexities of OAuth 2.0 in MCP

Right, but there is a snag. OAuth 2.0 is a little bit complicated by default, and certainly in the MCP server context, the way that it's wound into the MCP spec is a little bit convoluted. Because these standards are changing all the time, there's no tooling available for this yet. So, developers right now are still basically on their own when it comes to integrating this.

Okay, I understand. So, while OAuth 2.0 is the standard, its integration within the MCP spec is complex, and the lack of existing tools makes it challenging for developers to implement. This is where a library like @civic/auth-mcp comes in, as it simplifies this process, right?

Exactly, it greatly simplifies it. It offers a one-line integration on the server side to wrap your MCP server in, and it offers options on the client side depending on what your MCP client needs are. I want to emphasize the simplicity on the server side.

That's a significant benefit for developers.

The one-line integration on the server side is particularly straightforward if you want to use Civic Auth. Civic Auth is itself one of the simplest and fastest ways to add authentication to a traditional app, and now with @civic/auth-mcp, it becomes the simplest and fastest way to add authentication to an MCP server. In addition to that, you can also adapt it for other OIDC providers.

That's right! It makes it incredibly easy to add authentication to your MCP server, designed to be simple, fast, and flexible.

Addressing the Client-Side Challenge in MCP Authentication

We've talked a lot about securing the server, but what about the clients? You mentioned earlier that an MCP server requiring auth is no good if nothing can consume it. How do MCP clients fit into this picture, especially since they differ from traditional clients like web browsers?

Yes, MCP clients are an important challenge here. There's a limit to what they are capable of doing compared to, say, a browser. At the moment, MCP clients are agents like Claude Desktop from Anthropic, which is running on your machine and able to execute tool calls. There are also development assistants such as Cursor or Windsurf. These clients operate in constrained environments—they're not full web browsers with all the UI capabilities and session management that traditional OAuth flows expect.

So, we have these specialized tools. How does their nature affect how they handle authentication, especially as they move towards these phase two, internet-accessible MCP servers?

Currently, they really only work with phase one MCP servers. But as they adapt to using phase two MCP servers, they have to answer the question: if the MCP server requires an OAuth access token, how do they get that access token? They don't have the same capabilities as a web browser, and depending on the context in which they're run, how they obtain these tokens may be very different. Each client type—desktop applications, CLI tools, backend services—has its own constraints and capabilities when it comes to handling authentication flows.

What are some of the ways these clients can obtain tokens?

The simplest case, and one of the cases supported in the @civic/auth-mcp library, is a command-line tool. Similar to running something like Claude Desktop, you're running a command on your local machine, and it can open a browser on your local machine. That browser can send you through the login process.

That makes sense for local applications. What about other scenarios?

You might imagine an MCP server that is running on a backend. So, somebody has a web app, and that web app's backend wants to incorporate an LLM. In that case, the client—the backend—really just needs to be able to obtain the token; it can delegate to the front end of that web app to go through the OAuth process.

So, the user experience can still be managed through a familiar web interface.

That's right. But there are more exotic examples. In general, I think it's a mistake to expect us to be able to fit this tool calling neatly into the existing paradigms of how we use web apps and desktop apps. We don't want to be putting authorization and login screens in front of users very often. We need a more sophisticated way to handle authorization.

The Future: Sophisticated Authorization and Broader Possibilities

It sounds like there's a need for more advanced solutions.

Yes, and a lot of other things relating to security and granularity of permission scopes. These are all things that Civic is thinking very deeply about right now, and I'd love people to get in touch with us to find out more about what we're building in that space. I want to start to tease here a few powerful features that could be possible once you have a sophisticated MCP client and server architecture, in terms of allowing the power of tool calling and MCP.

The future of MCP authentication extends far beyond simple login flows—we're looking at contextual permissions, dynamic scoping, and seamless user experiences that don't interrupt AI workflows with constant authorization prompts.

Conclusion

The evolution of MCP servers from local development tools to internet-accessible services represents a fundamental shift in how AI agents interact with real-world systems, but this transition demands robust authentication solutions that current tooling doesn't adequately address. Libraries like @civic/auth-mcp bridge this gap by simplifying OAuth 2.0 integration, enabling developers to secure their MCP servers without getting bogged down in complex authentication protocols. As we move toward more sophisticated AI workflows, the authentication challenge is just the first step in building truly secure, scalable, and user-friendly AI agent ecosystems.

Get Involved and Share Your Feedback

We're actively seeking feedback from the developer community on the @civic/auth-mcp library. Whether you're building MCP servers, working with AI agents, or exploring authentication solutions, your input is valuable.

Try the library: @civic/auth-mcp

Join the discussion: Share your experiences, questions, and suggestions in our Discord. 

Your feedback helps shape the future of MCP authentication and ensures these tools meet real-world developer needs.

About the Author

Daniel Kelleher is the Chief Technology Officer at Civic. With a decade of experience in the fields of finance, e-justice and blockchain, Dan holds a Ph.D. in computer science from Trinity College, Dublin. He is dedicated to finding trustworthy, secure and decentralized technological solutions to improve the lives of people around the world and resides in Berlin, Germany.

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