M365 Agent MCP

A remote MCP server for ChatGPT workspace agents. One Vercel deployment serves multiple agents, and each agent gets access only to the Microsoft 365 mailbox mapped to its secret URL key.

Mailboxes

This project is configured for these three agent mailboxes:

• reservations@kwantu.co.za
• assistant@kwantu.co.za
• assistant@sapphireglobalfs.com

All three mailboxes must exist in the Microsoft 365 tenant identified by TENANT_ID. If one mailbox is in a different tenant, use a separate deployment for that tenant.

Route Shape

Each MCP URL has this shape:

https://<vercel-domain>/api/agents/<agent-key>/mcp

The app route is:

app/api/agents/[agent]/[transport]/route.ts

<agent-key> is a long random secret. The server resolves it through AGENT_MAILBOX_MAP; unknown keys return HTTP 404.

Tools

• list_recent_emails: lists recent messages from the mapped mailbox.
• search_emails: searches messages in the mapped mailbox.
• read_email: reads one message from the mapped mailbox.
• send_email: sends HTML email from the mapped mailbox.

No database is used. Secrets and mailbox mapping live only in environment variables.

Microsoft Graph Setup

In Microsoft Entra admin center:

1. Create an app registration.
2. Create a client secret and copy the secret value immediately.
3. Add Microsoft Graph application permissions:
   • Mail.Read
   • Mail.Send
4. Grant admin consent for the tenant.

Recommended tenant safety control: restrict the app to only the three agent mailboxes with an Exchange Online application access policy.

Connect-ExchangeOnline

New-DistributionGroup `
  -Name "M365 Agent MCP Mailboxes" `
  -Alias "m365-agent-mcp-mailboxes" `
  -Type Security `
  -PrimarySmtpAddress "m365-agent-mcp-mailboxes@kwantu.co.za"

Add-DistributionGroupMember -Identity "m365-agent-mcp-mailboxes@kwantu.co.za" -Member "reservations@kwantu.co.za"
Add-DistributionGroupMember -Identity "m365-agent-mcp-mailboxes@kwantu.co.za" -Member "assistant@kwantu.co.za"
Add-DistributionGroupMember -Identity "m365-agent-mcp-mailboxes@kwantu.co.za" -Member "assistant@sapphireglobalfs.com"

New-ApplicationAccessPolicy `
  -AppId "<CLIENT_ID>" `
  -PolicyScopeGroupId "m365-agent-mcp-mailboxes@kwantu.co.za" `
  -AccessRight RestrictAccess `
  -Description "Restrict M365 Agent MCP to approved agent mailboxes"

Test-ApplicationAccessPolicy -Identity "reservations@kwantu.co.za" -AppId "<CLIENT_ID>"
Test-ApplicationAccessPolicy -Identity "assistant@kwantu.co.za" -AppId "<CLIENT_ID>"
Test-ApplicationAccessPolicy -Identity "assistant@sapphireglobalfs.com" -AppId "<CLIENT_ID>"

Use a different PrimarySmtpAddress for the security group if kwantu.co.za is not an accepted domain in the tenant.

Environment Variables

Set these four variables in Vercel:

TENANT_ID=<directory-tenant-id>
CLIENT_ID=<application-client-id>
CLIENT_SECRET=<client-secret-value>
AGENT_MAILBOX_MAP={"<reservations-key>":"reservations@kwantu.co.za","<kwantu-assistant-key>":"assistant@kwantu.co.za","<sapphire-assistant-key>":"assistant@sapphireglobalfs.com"}

For local development, copy .env.example to .env.local and replace the placeholders.

1. Generate One Random Key Per Agent

From a terminal:

node -e "const crypto=require('crypto'); for (const name of ['reservations','kwantu-assistant','sapphire-assistant']) console.log(name + '=' + crypto.randomBytes(24).toString('hex'))"

Example output shape:

reservations=<reservations-key>
kwantu-assistant=<kwantu-assistant-key>
sapphire-assistant=<sapphire-assistant-key>

Then create the JSON map:

{
  "<reservations-key>": "reservations@kwantu.co.za",
  "<kwantu-assistant-key>": "assistant@kwantu.co.za",
  "<sapphire-assistant-key>": "assistant@sapphireglobalfs.com"
}

When entering AGENT_MAILBOX_MAP in Vercel, paste it as one line with no outer quotes.

2. Set The Four Environment Variables In Vercel

In Vercel:

1. Open the project.
2. Go to Settings, then Environment Variables.
3. Add TENANT_ID, CLIENT_ID, CLIENT_SECRET, and AGENT_MAILBOX_MAP.
4. Apply them to Production, Preview, and Development if you want all environments to work.

With the Vercel CLI, you can also run:

vercel env add TENANT_ID production
vercel env add CLIENT_ID production
vercel env add CLIENT_SECRET production
vercel env add AGENT_MAILBOX_MAP production

Repeat for preview and development if needed.

3. Deploy

Install dependencies and verify the build:

npm install
npm run build

Deploy:

vercel --prod

Or push the repo to GitHub and import it into Vercel, then deploy from the Vercel dashboard.

4. Get The Per-Agent MCP URLs

After deployment, use your Vercel production domain and each generated key:

Reservations agent:
https://<vercel-domain>/api/agents/<reservations-key>/mcp

Kwantu assistant agent:
https://<vercel-domain>/api/agents/<kwantu-assistant-key>/mcp

Sapphire assistant agent:
https://<vercel-domain>/api/agents/<sapphire-assistant-key>/mcp

Paste the relevant URL into each ChatGPT workspace agent as its custom MCP server URL.

Local Run

npm install
Copy-Item .env.example .env.local
npm run dev

Local MCP URL:

http://localhost:3000/api/agents/<agent-key>/mcp

The health page is available at:

http://localhost:3000

Validation Checklist

• Unknown agent key returns HTTP 404.
• Each known key can list/read only its mapped mailbox.
• send_email sends from the mapped mailbox and saves to Sent Items.
• Exchange Online application access policy test passes for the three allowed mailboxes.
• Exchange Online application access policy test fails for an unrelated mailbox.

Client Secret Renewal

Client secrets expire. Before expiry, create a new secret in the app registration, update CLIENT_SECRET in Vercel, and redeploy.