yusukebe · yusukebe · Jun 19, 2025 · Jun 17, 2025 · Jun 17, 2025 · Jun 18, 2025
diff --git a/package.json b/package.json
@@ -14,8 +14,8 @@
   "license": "MIT",
   "dependencies": {
     "@hono/graphql-server": "^0.4.1",
+    "@hono/mcp": "^0.1.0",
     "@modelcontextprotocol/sdk": "^1.12.1",
-    "fetch-to-node": "^2.1.0",
     "graphql": "^16.6.0",
     "hono": "^4.7.11",
     "zod": "^3.25.7"

diff --git a/src/mcp.ts b/src/mcp.ts
@@ -1,8 +1,8 @@
+import { StreamableHTTPTransport } from '@hono/mcp'
 import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js'
-import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js'
-import { toFetchResponse, toReqRes } from 'fetch-to-node'
 import type { Context } from 'hono'
 import { Hono } from 'hono'
+import { HTTPException } from 'hono/http-exception'
 import { z } from 'zod'
 import type { Env } from './app'
 import { getShop, getShopPhotosWithData, listShopsWithPager } from './app'
@@ -69,38 +69,20 @@ export const getMcpServer = async (c: Context<Env>) => {
 
 const app = new Hono<Env>()
 
-app.post('/', async (c) => {
-  const { req, res } = toReqRes(c.req.raw)
+app.all('/', async (c) => {
   const mcpServer = await getMcpServer(c)
-  const transport: StreamableHTTPServerTransport =
-    new StreamableHTTPServerTransport({
-      sessionIdGenerator: undefined,
-    })
+  const transport = new StreamableHTTPTransport()
   await mcpServer.connect(transport)
-  await transport.handleRequest(req, res, await c.req.json())
-  res.on('close', () => {
-    transport.close()
-    mcpServer.close()
-  })
-  return toFetchResponse(res)
+  return transport.handleRequest(c)
 })
 
-app.on(['GET', 'DELETE'], '/', (c) => {
-  return c.json(
-    {
-      jsonrpc: '2.0',
-      error: {
-        code: -32000,
-        message: 'Method not allowed.',
-      },
-      id: null,
-    },
-    405
-  )
-})
+app.onError((err, c) => {
+  console.log(err.message)
+
+  if (err instanceof HTTPException && err.res) {
+    return err.res
+  }
 
-app.onError((e, c) => {
-  console.error(e.message)
   return c.json(
     {
       jsonrpc: '2.0',

diff --git a/test/mcp.test.ts b/test/mcp.test.ts
@@ -236,6 +236,37 @@ describe('Test /mcp', () => {
     expect(content).toHaveProperty('mimeType', 'image/jpeg')
     expect(typeof content.data).toBe('string')
   })
+
+  it('Should throw an error for get_shops tool', async () => {
+    const res = await app.request(
+      '/mcp',
+      {
+        method: 'POST',
+        body: JSON.stringify({
+          jsonrpc: '2.0',
+          id: 6,
+          method: 'tools/call',
+          params: {
+            name: 'get_shops',
+            arguments: {},
+          },
+        }),
+        headers: {
+          'Content-Type': 'application/json',
+          Accept: 'application/json, text/event-stream',
+        },
+      },
+      mockEnv
+    )
+
+    const messages = await parseSSEJSONResponse(res)
+    const result = messages.find((m) => m.id === 6)
+
+    expect(res.status).toBe(200)
+    expect(result).toHaveProperty('error')
+    expect(result.error.code).toBe(-32602)
+    expect(result.error.message).toContain('Invalid arguments for tool get_shops')
+  })
 })
 
 export async function parseSSEJSONResponse(res: Response) {

diff --git a/yarn.lock b/yarn.lock
@@ -378,6 +378,11 @@
   dependencies:
     graphql "^16.5.0"
 
+"@hono/mcp@^0.1.0":
+  version "0.1.0"
+  resolved "https://registry.yarnpkg.com/@hono/mcp/-/mcp-0.1.0.tgz#be5b1af6d0a271b669cf477cede0e5448bf78117"
+  integrity sha512-IELNnKF5tjbUm+wthfToZrNxZIjs1RWLiwCx8N+m8xfJcL6hfcpj/21Gsw8HL88lbnCh191mbFwYvXnx856QZg==
+
 "@humanwhocodes/config-array@^0.11.13":
   version "0.11.14"
   resolved "https://registry.npmjs.org/@humanwhocodes/config-array/-/config-array-0.11.14.tgz"
@@ -1765,11 +1770,6 @@ fdir@^6.4.4:
   resolved "https://registry.npmjs.org/fdir/-/fdir-6.4.5.tgz"
   integrity sha512-4BG7puHpVsIYxZUbiUE3RqGloLaSSwzYie5jvasC4LWuBWzZawynvYouhjbQKw2JuIGYdm0DzIxl8iVidKlUEw==
 
-fetch-to-node@^2.1.0:
-  version "2.1.0"
-  resolved "https://registry.yarnpkg.com/fetch-to-node/-/fetch-to-node-2.1.0.tgz#e779d699f80aea0b1b34fd057737d151cb1dc19e"
-  integrity sha512-Wq05j6LE1GrWpT2t1YbCkyFY6xKRJq3hx/oRJdWEJpZlik3g25MmdJS6RFm49iiMJw6zpZuBOrgihOgy2jGyAA==
-
 file-entry-cache@^6.0.1:
   version "6.0.1"
   resolved "https://registry.npmjs.org/file-entry-cache/-/file-entry-cache-6.0.1.tgz"