ClosedMCP
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Accept ClosedMCP sign-in in your tool

Wrap your MCP server with our SDK, then decide which customers can use it.

Using an SDK? → SDK reference

Start with our SDK

Install our SDK. Wrap your MCP server. Every request now comes with the signed-in person.

v0.1.1
Install
npm install @closedmcp/sdk @modelcontextprotocol/sdk
TypeScript example
import { McpServer } from
  "@modelcontextprotocol/sdk/server/mcp.js";
import {
  closedMcpPerson,
  serveWithClosedMcp,
} from "@closedmcp/sdk";

serveWithClosedMcp(() => {
  const mcp = new McpServer({
    name: "hello", version: "1.0.0",
  });
  mcp.registerTool("hello", { inputSchema: {} },
    async () => ({ content: [{
      type: "text",
      text: `Hello ${closedMcpPerson().email}`,
    }] }));
  return mcp;
}, {
  resource: "https://example.com/mcp",
  allowedDomains: ["example.com"],
});

Package page ↗Source ↗

Each request has a pass that identifies the signed-in person. The SDK checks the pass. Your tool decides what that person can do.

The 3 steps

  1. Wrap your server. Install the SDK above and set your public MCP URL and customer domains.
  2. Use the person in each tool. Read their email and company from the SDK’s person helper.
  3. Add your MCP URL in ClosedMCP. Open Add an MCP. Other companies can then install your tool.

See the complete SDK server example for a runnable Node.js server.

What a pass contains

A tool identity token is a JWT signed with Ed25519 (alg: EdDSA). Its kid names the key in the public key set.

iss
https://closedmcp.com. The same for every company.
aud
The server this token is for. Must match your MCP server URL (resource).
sub
The person’s stable ClosedMCP id.
email
The person’s work email.
domain
Their company’s domain, confirmed by Google Workspace at sign-in (Google’s hd equals it).
org
Their company’s ClosedMCP workspace.
client
The AI app they use, like Claude, when known. The app names itself, so show it but don’t rely on it for security.
iat, exp
When it was made and when it expires: 5 minutes at most.
jti
A unique id for this token.

ClosedMCP makes a fresh tool identity token for every call. It never sends your MCP server the person’s ClosedMCP key or their Google tokens. Your server receives only the tool identity token.

Rules your server must follow

  • Check every request. The SDK verifies the signature, issuer, audience, and expiry. It refuses missing or invalid passes.
  • Accept only your customers. Set ALLOWED_DOMAINS to the company domains you serve. A valid pass identifies a person; it does not make them your customer.
  • Check what each person may do. Use their sub or email for permissions in your service.
  • Do not store passes or send them elsewhere.

AI apps that connect directly

AI apps discover ClosedMCP through your server’s sign-in metadata. The SDK serves that metadata and verifies each pass they send.