AWS re:Invent 2025 - Compile blazing-fast MCP servers in Rust (DEV405)

Building Blazing-Fast MCP Servers with Rust

Overview

• Presenter is Darkco, an AWS developer advocate heavily involved in the Rust ecosystem
• Presentation covers building MCP (Model Coordination Protocol) servers using the Rust programming language
• MCP is an open protocol that allows language models and AI assistants to interact with tools and resources on a user's computer
• Rust is positioned as a superior alternative to Python and other languages for building MCP servers

Advantages of Rust for MCP Servers

• Rust binaries are compiled and self-contained, avoiding the pain of installing dependencies with tools like npm, pip, or cargo install
• Rust's type safety and compile-time guarantees provide a more robust and secure foundation for MCP servers
• Rust's performance characteristics enable building highly performant and responsive MCP servers

Anatomy of a Rust MCP Server

1. Server Struct: Defines the core MCP server, including a ToolRouter for mapping tools to handler functions
2. Tool Router Macro: Generates the necessary boilerplate for the ToolRouter implementation
3. Server Handler: Implements the required MCP server methods like call_tool and list_tools
4. Tool Functions: Implement the actual functionality exposed as MCP tools

Implementing MCP Tools

1. Tool Struct: Defines the input parameters for the tool using a Rust struct and the schemars crate for JSON schema validation
2. Tool Function: Implements the tool logic, potentially calling other helper functions to interact with external resources
3. Tool Macro: Decorates the tool function with metadata like the tool name and description

Integrating with External Resources

• Presenter demonstrates building an MCP server that interacts with a local to-do API and a thermal receipt printer
• The MCP server exposes tools to:
  • Retrieve the list of to-dos
  • Create a new to-do
  • Print the details of a specific to-do on the receipt printer

Tooling and Testing

• The presenter uses the just task runner for building and testing the MCP server
• The MCP Inspector is a TypeScript-based tool that can be used to connect to and test MCP servers

Real-World Applications

• The presenter shares examples of other Rust-based MCP servers they have built, including:
  • An "IM Policy Autopilot" MCP server that generates IAM policies based on code analysis
  • A "Grimmoire" MCP server that stores and retrieves useful code snippets

Key Takeaways

• Rust provides a robust and performant foundation for building MCP servers, addressing the shortcomings of Python and other interpreted languages
• The Rust MCP SDK (RMCP) simplifies the process of creating MCP servers by providing macros and abstractions
• Integrating MCP servers with external resources like APIs and hardware devices is straightforward in Rust
• Rust's tooling, like the just task runner and the MCP Inspector, facilitate development and testing of MCP servers