Build MCP servers as WebAssembly components

Ian McDonald - Extend / Corey Ryan - fastertools

The Model Context Protocol is USB-C for AI applications. While MCP servers are typically sandboxed via containers or VMs, WebAssembly components offer an alternative with unique benefits. Wasmcp

Wasmcp is a framework for developing MCP servers as Wasm components and composing them together for reuse.

It lets you:

• Build composable MCP servers as WebAssembly components.
• Mix tools and features written in Rust, Python, TypeScript, etc. in a single server binary.
• Plug in shared components for authorization, sessions, logging, and more across multiple MCP servers.
• Run the same sandboxed MCP server binary locally, on the network edge via Fermyon Wasm Functions, on Kubernetes clusters (e.g. via SpinKube), or on any runtime that speaks WASI + components.
• Expose both stdio and Streamable HTTP transports via standard WASI exports.

Why?

We built wasmcp because we want to run agent-facing applications at scale in a future where MCP is the foundation for distributed intelligent systems. That means enabling powerful new MCP servers that are first-class applications rather than just proxies for REST APIs. Wasmcp is a step toward a polyglot AI application architecture that works consistently across local, cloud, and self-hosted platforms.