Plugin

The package exposes two Elysia plugins. Use mcp() for the normal application setup. Use withMcpMethods() only when a feature plugin must register standalone primitives before the application mounts the MCP endpoint.

mcp

function mcp(options?: McpPluginOptions): Elysia

import { mcp } from '@mwillbanks/elysia-mcp-adapter'
import { Elysia } from 'elysia'

const app = new Elysia().use(
  mcp({
    server: {
      name: 'billing-api',
      version: '1.0.0'
    },
    path: '/mcp',
    allowedRoutes: '*'
  })
)

mcp() installs .mcpTool(), .mcpResource(), and .mcpPrompt(), discovers eligible routes, and mounts the JSON-RPC transport.

Server metadata

Response marshaling

Tool annotations

Annotations tell MCP clients about behavioral properties. They do not replace application authorization.

Shared metadata and icons

withMcpMethods

function withMcpMethods(): Elysia

new Elysia()
  .use(withMcpMethods())
  .mcpTool('health.read', () => ({ ok: true }))
  .use(mcp())

The plugin augments the Elysia instance without mounting /mcp. A later mcp() call reuses those explicit registrations and adds the endpoint.

Naming helpers

The package also exports:

function sanitizeMcpName(value: string): string
function defaultOperationNameResolver(operation: McpRouteOperation): string

sanitizeMcpName() converts an arbitrary name into the MCP-compatible form. defaultOperationNameResolver() prefers detail.operationId, then derives a stable name from the HTTP method and path.

See Configuration for production defaults and Route-backed Tools for the per-route contract.