In the fast-evolving world of AI and software development, bridging backend logic with AI frontends is crucial for building powerful and context-aware applications. If you’re a Rust enthusiast looking to integrate Rust-based logic with AI frontends using the Model Context Protocol (MCP), this guide is for you.

What is MCP?

MCP, or Model Context Protocol, is an open protocol designed to standardize how applications provide context to Large Language Models (LLMs). As described on the MCP official website:

MCP is an open protocol that standardizes how applications provide context to LLMs.

Essentially, MCP enables seamless interaction between applications and LLMs by providing a structured and consistent way to pass information (context). This allows developers to integrate local data sources, business logic, or any other backend services with LLM-powered frontends.

Key Features of MCP

• Standardization: MCP provides a universal framework for connecting applications to LLMs, reducing the complexity of integration.
• Flexibility: It supports various programming languages and platforms, making it adaptable for diverse tech stacks.
• Client Ecosystem: MCP clients like Claude Desktop (check out other MCP clients) make it easy to consume context in AI frontends.

For a deeper dive into MCP’s architecture, check out the general MCP architecture page.

The following case highlights using a local data source that is available via Rust code

^{source: general MCP architecture}

While MCP has official SDKs for popular programming languages such as Python, TypeScript, Java, Kotlin, and C#, Rust currently lacks an official SDK. However, this doesn’t mean Rust developers are left in the lurch. By leveraging Rust’s strengths and WebAssembly (wasm), you can still make your Rust code accessible to MCP clients like Claude Desktop.

Why Rust?

Rust is a modern systems programming language known for its performance, memory safety, and concurrency. It’s a favorite among developers for scenarios where reliability and efficiency are paramount. Here are some reasons why Rust is an excellent choice for MCP integrations:

• Concurrency. Rust’s ownership model and borrowing rules eliminate data races at compile time, ensuring safe concurrent programming. This makes Rust ideal for building high-performance systems that handle multiple threads or tasks simultaneously.
  
• Memory Safety Without Garbage Collection. Unlike languages like Java or Python that rely on garbage collection, Rust uses a unique ownership system to manage memory. This gives developers precise control over memory allocation and deallocation, which is critical for resource-intensive applications.
  
• Cargo Package Manager. Rust’s package manager, Cargo, simplifies dependency management, building, and testing. The ecosystem is rich with high-quality libraries for tasks like serialization, hashing, multithreading, and more. This robust ecosystem can streamline MCP-related development.
  
• Zero-cost abstractions. Rust allows you to write high-level abstractions without incurring runtime performance penalties, making it both expressive and efficient.
  
• Pattern matching. This powerful language feature enables developers to concisely and effectively match complex data structures against specific patterns to extract and handle different cases or scenarios in a clean and readable manner.
  
• Web Development with Rust Rust’s growing popularity in web development is evident with frameworks like Rocket and tools like wasm-bindgen, which bridge Rust with JavaScript. This tool makes it easy to expose Rust logic to the web or integrate it with JavaScript-based MCP clients.

Source code

You can find the source code on GitHub: https://gh.com/ls/mcp-server-rust

Practical Example: Using Rust with MCP Clients

In this guide, we’ll demonstrate how to integrate a simple Rust function with an MCP client. While this example uses a basic factorial function, the same principles can be applied to more complex Rust logic.

Showcasing the Functionality: Rust Meets MCP

Here’s a simple implementation of a factorial function in Rust:

#[wasm_bindgen]
pub fn factorial(num: u64) -> u64 {
    let mut result = 1;
    for i in 1..=num {
        result *= i;
    }
    result
}

^source

To demonstrate how Rust logic can be integrated with MCP clients, we use a simple factorial function. While this example is straightforward—most MCP clients can easily calculate factorials without external support—it serves as a foundational showcase for embedding Rust logic into AI workflows.

Converting Rust Code to JavaScript

Since MCP clients like Claude Desktop rely on JavaScript environments, the Rust code must be converted into JavaScript. This transformation is achieved using WebAssembly (Wasm), which allows Rust code to run in environments where JavaScript is supported. However, it’s important to note that once converted, some advantages Rust has over JavaScript may not fully apply in this context.

Building the Rust and TypeScript Code

• Building the Rust Code: Use the command npm run build:wasm:release to compile the Rust code into a Wasm module.
• Setting Up TypeScript: Run npm install to set up TypeScript dependencies. Refer to other scripts in the package.json file for additional configurations.

Importing the Generated JavaScript Code

Once the Rust code has been compiled into WebAssembly, it can be imported into your JavaScript or TypeScript project. For example:

import init, { factorial } from "./lib/rust-functions-lib/pkg/rust_funcations_lib.js";

^source

This imports the factorial function (originally written in Rust) and the init function for initializing the wasm module.

Handling the Initialization Process

To avoid common errors related to wasm initialization, the init function must be called with the appropriate configuration. Here’s an example:

const wasmPath = fileURLToPath(new URL("./lib/rust-functions-lib/pkg/rust_funcations_lib_bg.wasm", import.meta.url));
const wasmBytes = await readFile(wasmPath); // Read the wasm file from the filesystem
await init(wasmBytes); // Initialize the wasm module with the file contents

^source

This approach ensures the wasm module is properly loaded into memory before use.

Common Errors and Their Solutions

• TypeError: fetch failed
  An init() (note the empty parameter list) call likely causes a “TypeError: fetch failed” error.
  The error occurs because the fetch API is not implemented in the Node.js environment by default, and the wasm module (rust_funcations_lib.js) is trying to use it. This is a common issue when using wasm modules that rely on fetch for loading resources.
  • Solution: Use the readFile method (as shown above) to load the .wasm file directly from the filesystem, bypassing the need for fetch.
• TypeError(node-fetch cannot load ${url}
  “TypeError: node-fetch cannot load file:///…/rust_funcations_lib_bg.wasm. URL scheme “file” is not supported.”
  The rust_funcations_lib.js file is a JavaScript wrapper generated by wasm-pack tool kit. It dynamically loads the .wasm file (rust_funcations_lib_bg.wasm) at runtime using the fetch API. The fetch API in node-fetch does not support the file.
  • Solution: Explicitly read the .wasm file from the filesystem using use fs (Node.js’s file system module) and pass its contents to the init function as bytes,

Recording

Conclusion

Integrating Rust logic with MCP clients opens up exciting possibilities. Although Rust lacks an official MCP SDK at the time of writing, its compatibility with WebAssembly provides a practical workaround. By leveraging wasm, Rust code can be seamlessly executed in JavaScript environments, enabling developers to bridge the gap between Rust’s powerful capabilities and the AI-driven workflows facilitated by MCP clients.

Whether you’re creating custom AI integrations or harnessing local data sources, Rust’s flexibility and MCP’s standardization offer a robust foundation for innovation.

Ultimately, MCP opens the door to standardized communication with AI models, while Rust ensures the backend logic is fast, safe, and scalable. With careful handling of wasm initialization and compatibility issues, developers can combine the best of both worlds to create cutting-edge applications that leverage the power of modern protocols and programming paradigms.

update 2024 12 22

VS code can be a MCP client as well: