Fix `Error: redisUrl is required`

🚧 This PR is Part of a Series

• https://github.com/vercel-labs/mcp-for-next.js/pull/17
• https://github.com/vercel/mcp-adapter/pull/62

👋 TL;DR

Fix Error: redisUrl is required

🔎 Details

resolves https://github.com/vercel-labs/mcp-for-next.js/issues/16

MCP Server

• pnpm add dotenv@latest
• add lib/env.ts for loading REDIS_URL
• extend route.ts to pass redisUrl to @vercel/mcp-adapter#createMcpServer param Config[redisUrl] https://github.com/vercel/mcp-adapter/blob/7149159/src/next/mcp-api-handler.ts#L75
• add .nvmrc (lts/*)

MCP Client

• pnpm add -D @modelcontextprotocol/sdk@latest
• extend package.json#scripts (test:client)

✅ How to Test

1. run:

   #/usr/bin/env bash
   nvm install
   nvm use
   pnpm install -D
   
   # https://github.com/redis/node-redis/blob/9ea260f/packages/client/lib/client/index.ts#L33
   # replace `redis[s]://[[username][:password]@][host][:port][/db-number]` with your actual `REDIS_URL`
   echo "REDIS_URL=\"redis[s]://[[username][:password]@][host][:port][/db-number]\"" > .env.local
   
   pnpm build
   pnpm dev

2. in another terminal, run pnpm test:client http://localhost:3000
3. 🔴 see that the output no longer reads:

   > next.js-mcp-server@0.1.0 dev /Users/patrick/src/servant-io/mcp-for-next.js
   > next dev
   
      ▲ Next.js 15.2.4
      - Local:        http://localhost:3000
      - Network:      http://192.168.1.52:3000
   
    ✓ Starting...
    ✓ Ready in 2.8s
    ○ Compiling /[transport] ...
    ✓ Compiled /[transport] in 1443ms (994 modules)
   Error: redisUrl is required
       at Generator.next (<anonymous>)
       at new Promise (<anonymous>)
       at Generator.next (<anonymous>)
       at new Promise (<anonymous>)
       at new Promise (<anonymous>)
    ⨯ unhandledRejection: Error: redisUrl is required
       at Generator.next (<anonymous>)
       at new Promise (<anonymous>)
       at Generator.next (<anonymous>)
       at new Promise (<anonymous>)
       at new Promise (<anonymous>)
    ⨯ unhandledRejection:  Error: redisUrl is required
       at Generator.next (<anonymous>)
       at new Promise (<anonymous>)
       at Generator.next (<anonymous>)
       at new Promise (<anonymous>)
       at new Promise (<anonymous>)

4. 🟢 instead, see that the output now reads:

   > next.js-mcp-server@0.1.0 dev /Users/patrick/src/servant-io/mcp-for-next.js
   > next dev
   
      ▲ Next.js 15.2.4
      - Local:        http://localhost:3000
      - Network:      http://192.168.1.52:3000
      - Environments: .env.local
   
    ✓ Starting...
    ✓ Ready in 1650ms
    ○ Compiling /[transport] ...
    ✓ Compiled /[transport] in 1458ms (999 modules)
   Redis error [Error: Socket closed unexpectedly]
   Redis error [Error: Socket closed unexpectedly]
   Redis error [Error: Socket closed unexpectedly]

🥜 GIF