isBusinessEmail

Connect Claude, ChatGPT, Cursor, VS Code and other MCP clients to isBusinessEmail: server URL, OAuth sign-in, tools, example prompts and limits.

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isBusinessEmail runs a remote MCP server (Model Context Protocol). Connect it once, and your AI assistant can check whether an address is a work email, classify a list of leads or find out whether a company runs Google Workspace or Microsoft 365, using your account and quota.

https://api.isbusinessemail.com/mcp

Transport	Streamable HTTP (JSON responses, no sessions)
Sign-in	OAuth 2.1 with PKCE, through your isBusinessEmail account. Or send an API key as a Bearer token.
Cost	Free. Each check counts toward your daily quota, like an API call.

Connect your assistant

Claude (web, desktop and mobile)

1. Open Settings → Connectors and choose Add custom connector.
2. Name it isBusinessEmail and paste https://api.isbusinessemail.com/mcp as the URL.
3. Select Connect, sign in to isBusinessEmail (or create a free account) and select Allow access.

On Team and Enterprise plans, an owner adds the connector for the organization first.

Claude Code

claude mcp add --transport http isbusinessemail https://api.isbusinessemail.com/mcp

Then run /mcp inside Claude Code and choose Authenticate. A browser window opens for sign-in.

ChatGPT

Add a custom connector (in developer mode, depending on your plan) with the server URL https://api.isbusinessemail.com/mcp and OAuth authentication. ChatGPT registers itself and opens the sign-in page.

Cursor

~/.cursor/mcp.json (or .cursor/mcp.json in a project):

{
  "mcpServers": {
    "isbusinessemail": { "url": "https://api.isbusinessemail.com/mcp" }
  }
}

Cursor shows Needs login next to the server; select it to sign in.

VS Code

.vscode/mcp.json:

{
  "servers": {
    "isbusinessemail": { "type": "http", "url": "https://api.isbusinessemail.com/mcp" }
  }
}

Any other client, with an API key

If your client can’t do OAuth, use a secret key from your dashboard as a header:

{
  "mcpServers": {
    "isbusinessemail": {
      "url": "https://api.isbusinessemail.com/mcp",
      "headers": { "Authorization": "Bearer ibe_live_your_key" }
    }
  }
}

Keep keys out of shared repositories. An OAuth connection is safer: it creates its own key that you can revoke without touching your other integrations.

Tools

Tool	What it does	Counts as
check_email	Classifies one address: category, is_business, recommendation, reasons, typo suggestion, mail provider, Google Workspace / Microsoft 365	1 check
check_domain	The same for a domain, for when you only care about the company	1 check
check_batch	Up to 100 addresses or domains in one call, results in input order	1 check per item
get_usage	Tier, limits, checks used and remaining today, last 30 days	free
report_wrong_verdict	Reports a misclassified address or domain; a person reviews it	free (50 a day)

The check tools take an optional policy (b2b, strict or lenient; see Categories and policies). Every tool returns a short text summary for the assistant and the full API response as structured content, with the same fields as POST /v1/check.

Things to ask

• “Is [email protected] a work email? Does Acme use Google Workspace or Microsoft 365?”
• “Here are 40 sign-ups from this week. Which ones are personal or disposable?”
• “Score these leads by email domain and tell me which to send to sales.”
• “Why was contoso.com classified as business? Show me the reasons.”
• “How many checks do I have left today?”

How sign-in works

The server follows the MCP authorization spec:

1. Without a token, /mcp answers 401 with a WWW-Authenticate header pointing at https://api.isbusinessemail.com/.well-known/oauth-protected-resource/mcp.
2. The client reads the authorization server’s metadata at https://api.isbusinessemail.com/.well-known/oauth-authorization-server, then registers itself (dynamic client registration).
3. You sign in at isbusinessemail.com and approve the app. PKCE (S256) is required.
4. The app receives a secret key named MCP · . It shows up in your keys, with its own usage. Revoke it there to disconnect the app. Connecting the same app again replaces its previous key.

Limits and privacy

• MCP checks use your account’s rate limits and daily quota. When the quota is used up, tools return a quota_exceeded error until 00:00 UTC.
• The MCP server sees the same data as the API: the addresses and domains your assistant sends. It never emails or probes them. See Privacy and data.
• Your assistant decides when to call a tool. Most clients ask before running tools; check your client’s settings.

Troubleshooting

Symptom	Fix
The client says the server needs authentication	Connect again and finish the sign-in in the browser.
“This account already has the maximum number of active API keys”	Revoke an unused key at /app/keys, then connect again.
Tools return quota_exceeded	Wait for the reset at 00:00 UTC, or ask for more.
Tools return invalid_token	The key was revoked. Connect again.