Build Your First Useful Business MCP Server

See what you are building

MCP stands for Model Context Protocol. It is a standard way for an AI application to discover approved information and narrowly described tools. It does not make every business system available to an AI.

Codex is the host. The MCP connection is the client that carries structured requests and results. Your local program is the server that decides what is technically possible.

The server uses STDIO: Codex starts the program and speaks through its input and output streams. It is not a public website and does not listen on a network port.

Draw the safety boundary first

When someone asks about the fictional business, return only approved profile, service and service-area facts. If the information is absent, say that a person must review it. Do not take an external action.

A local MCP startup command runs software on your computer with the privileges of the application that launched it. Read an unfamiliar command and its source before approving it. Here, you build the source and can see every file it reads.

Install the free foundations

These instructions use Windows PowerShell. The project files are the same on macOS or Linux, but paths and install commands differ.

Copynode --version
npm --version
npx --version

CopySet-Location "$env:USERPROFILE\Documents"
New-Item -ItemType Directory -Name business-facts-mcp
Set-Location .\business-facts-mcp
Get-Location

npm installs project packages. npx can run a package temporarily. If a version command fails, stop here and use the troubleshooting chapter.

Create the project and approved information

Run these commands from the empty business-facts-mcp folder. Versions are pinned to the combination that passed this guide’s six-test suite on August 1, 2026.

Copynpm init -y
npm install @modelcontextprotocol/server@2.0.0 zod@4.4.3
npm install -D @modelcontextprotocol/client@2.0.0 @types/node@26.1.2 typescript@7.0.2
New-Item -ItemType Directory -Name src
New-Item -ItemType Directory -Name data
New-Item -ItemType Directory -Name test
code .

If code is not recognized, open Visual Studio Code normally, choose File → Open Folder, and select business-facts-mcp.

After setup, the project should have this shape:

The JSON files hold the approved facts. The server code controls how those facts may be exposed. A future owner can update an approved service without rewriting the server.

Build the server and profile resource

Create src\server.ts or use the starter version. It imports Node’s file reader, the MCP server class, the local STDIO transport and Zod for input validation.

The helper readJson reads only a named file from this project’s data folder. The server instructions explicitly prohibit invented prices, availability, bookings, promises and service areas.

Copyserver.registerResource(
  "business-profile",
  "business://profile",
  {
    title: "Approved business profile",
    description: "Fictional public business facts for this learning exercise.",
    mimeType: "application/json",
  },
  async (uri) => {
    const business = await readJson("business.json");
    return {
      contents: [{
        uri: uri.href,
        mimeType: "application/json",
        text: JSON.stringify(business, null, 2),
      }],
    };
  },
);

A resource is reference information a host can read. Reading this profile does not change anything. The complete source file in the starter also registers the tools and starts the transport.

Add two useful read-only tools

A tool accepts structured input and performs one described operation. Zod rejects missing or malformed input before the handler does any work.

Copyannotations: {
  readOnlyHint: true,
  destructiveHint: false,
  openWorldHint: false,
}

Annotations help a client understand a tool’s consequence. They do not create safety by themselves: the actual handler must remain read-only. The starter handlers read local files, filter or compare values, and return structured results. They do not write files, access a network or contact anyone.

Build it without breaking STDIO

Compile the TypeScript and check that the server file exists:

Copynpm run build
Test-Path .\build\server.js

The build should return to the prompt without an error. The path check should print True.

If you run node build\server.js directly, the blank-looking terminal is normal: the server is waiting for an MCP client. Press Ctrl+C to stop it.

Test before an AI model is involved

MCP Inspector lets you inspect the resource and tools directly. Run it from the project folder:

Copynpx @modelcontextprotocol/inspector node build/server.js

The first run may download Inspector. A browser window should open; if it does not, open the local address printed in PowerShell.

Run the automated launch check

Copynpm test

A successful run ends with:

# tests 6
# pass 6
# fail 0

Starter verified: six tests passed

This is the observed result from the supplied starter on August 1, 2026. Do not continue to Codex if your local run shows a failure.

Install Codex and sign in with ChatGPT

The server and Inspector work without an AI account. Add Codex only after the server has passed its own checks.

Install on Windows

Copypowershell -ExecutionPolicy ByPass -c "irm https://chatgpt.com/codex/install.ps1 | iex"

The official npm alternative is:

Copynpm install -g @openai/codex

Close and reopen PowerShell, then check:

Copycodex --version
codex login

Choose Sign in with ChatGPT and complete the browser flow. This guide does not use an API key. ChatGPT sign-in uses subscription access when available; API-key sign-in is a separate usage-based path.

Copycodex login status

Official instructions may change. If the installer behaves differently, use the current OpenAI Codex CLI documentation.

Connect Codex and run the Launch Card

Return to the project folder, rebuild, and ask PowerShell for the exact compiled path:

Copynpm run build
$serverPath = (Resolve-Path .\build\server.js).Path
$serverPath
codex mcp add business-facts -- node $serverPath
codex mcp list
codex

The list should show business-facts. Inside Codex, type /mcp and confirm that the server is active.

MCP Server Launch Card

Troubleshoot, verify and extend safely

Advance one boundary at a time

Do not jump directly to email sending, live customer data, CRM changes or public hosting. Those steps need identity, authorization, privacy, activity records, error recovery and consequence-specific tests.

A useful MCP server is not the one with the most tools. It is the one whose information, actions and limits the business can explain and test.