Overview

@mwillbanks/elysia-mcp-adapter adds a Model Context Protocol HTTP endpoint to an Elysia application. Existing routes can become MCP tools, while explicit registration methods cover MCP-only tools, resources, resource templates, and prompts.

Preserve the Elysia lifecycle

Route-backed calls are converted into an internal Request and sent through app.handle(). This keeps the behavior that already protects and shapes your HTTP API:

• request parsing and TypeBox validation
• local hooks, guards, and authentication plugins
• error handlers and response mapping
• route-specific status codes and headers

The adapter never calls an Elysia route handler directly.

A focused MCP surface

The transport lives at POST /mcp by default and implements the core JSON-RPC methods for initialization, discovery, tool calls, resource reads, and prompt retrieval.

Design principles

1. Elysia is the application framework. The adapter adds protocol translation, not a parallel runtime.
2. JSON Schema stays JSON Schema. Route schemas are sanitized for transport without a TypeBox-to-Zod translation layer.
3. Exposure is deliberate. Tools are convenient by default; resources, prompts, headers, browser origins, and binary output require explicit configuration.
4. Protocol abstractions stay thin. No full MCP framework dependency is required.

Next steps

• Install the package
• Expose your first route
• Understand route-backed tools
• Harden the endpoint