Ext Auth
Extensions to authorization
What is Ext Auth?
Ext Auth is a Model Context Protocol (MCP) server that allows AI assistants like Claude, Cursor, and VS Code to extensions to authorization
Extensions to authorization
This server falls under the Security category on MCPgee, the world's largest MCP server directory with 33,000+ servers.
Features
- Extensions to authorization
Use Cases
Maintainer
Works with
Installation
Manual Installation
npx ext-authConfiguration
Configuration Details
claude_desktop_config.json
Performance
Response Metrics
Resource Usage
How to Set Up and Use Ext Auth
The MCP Authorization Extensions repository (modelcontextprotocol/ext-auth) defines optional, additive authorization specifications for the Model Context Protocol maintained by the official MCP project. It currently covers two extension drafts: OAuth Client Credentials flow for server-to-server machine authentication, and Enterprise-Managed Authorization for corporate environments with centralized identity providers. These extensions sit alongside the core MCP specification — implementations can adopt them independently without breaking core protocol behavior, making it the authoritative reference for developers who need to add authentication to MCP servers beyond what the base protocol defines.
Prerequisites
- Familiarity with the core MCP specification (modelcontextprotocol.io)
- Understanding of OAuth 2.0 flows (Client Credentials or enterprise SSO)
- An MCP server implementation to add authorization to
- Access to an OAuth 2.0 authorization server or enterprise identity provider if implementing the extensions
Read the core MCP specification
Before implementing authorization extensions, ensure you understand the base MCP specification at modelcontextprotocol.io. The ext-auth extensions are additive and assume a working MCP server.
Review the OAuth Client Credentials extension
Read the Client Credentials draft at the repository URL. This extension defines how MCP servers can require OAuth 2.0 client credentials (client_id + client_secret) from connecting clients — suitable for server-to-server integrations.
# Specification URL:
# https://github.com/modelcontextprotocol/ext-auth/blob/main/specification/draft/oauth-client-credentials.mdxReview the Enterprise-Managed Authorization extension
Read the Enterprise-Managed Authorization draft. This extension covers how organizations can delegate authorization decisions to a corporate identity provider (IdP) so that MCP servers respect enterprise access policies.
# Specification URL:
# https://github.com/modelcontextprotocol/ext-auth/blob/main/specification/draft/enterprise-managed-authorization.mdxImplement the chosen extension in your MCP server
Follow the specification's requirements for your server language/framework. Extensions are optional and composable — you can implement Client Credentials alone, Enterprise-Managed alone, or both together without conflicts.
Configure your MCP client with credentials
Update your MCP client configuration to include the credentials or tokens required by your server's chosen authorization extension. The exact config fields depend on which extension you implemented.
Ext Auth Examples
Client configuration
Example Claude Desktop MCP config for connecting to an authorization-protected MCP server using a bearer token. Adjust the env key names to match your server's expected authorization headers.
{
"mcpServers": {
"my-auth-server": {
"command": "node",
"args": ["/path/to/my-mcp-server/dist/index.js"],
"env": {
"MCP_CLIENT_ID": "your-client-id",
"MCP_CLIENT_SECRET": "your-client-secret"
}
}
}
}Prompts to try
After connecting to an authorization-protected MCP server, these prompts verify the connection is working and the server is enforcing access correctly.
- "List all tools available on this server"
- "Verify that I am authenticated and show my client identity"
- "What authorization scopes does this server require?"
- "Connect to the server and confirm the OAuth token is valid"Troubleshooting Ext Auth
MCP server returns 401 Unauthorized when the client connects
Ensure the client is providing credentials in the format expected by the extension. For Client Credentials, the client must exchange credentials for a token before connecting. Check the server logs to see which authorization header or token format it expects.
Enterprise-Managed Authorization fails with token validation errors
Verify that the token issuer URL matches the configured IdP, that the token has not expired, and that the client_id is registered with the enterprise IdP. Clock skew between server and IdP can also cause validation failures — ensure NTP is running on both.
Confusion about which extension version or draft to implement
Check the main branch of modelcontextprotocol/ext-auth for the latest draft. These are living specifications; always read the version tag or commit SHA noted in the specification file header to know exactly which revision you are implementing.
Frequently Asked Questions about Ext Auth
What is Ext Auth?
Ext Auth is a Model Context Protocol (MCP) server that extensions to authorization It connects AI assistants to external tools and data sources through a standardized interface.
How do I install Ext Auth?
Follow the installation instructions on the Ext Auth GitHub repository. Clone the repo, install dependencies, and add the server config to your AI client.
Which AI clients work with Ext Auth?
Ext Auth works with all major MCP-compatible AI clients including Claude Desktop, Claude Code, Cursor, VS Code (GitHub Copilot), Windsurf, and Cline.
Is Ext Auth free to use?
Yes, Ext Auth is open source and available under the MIT license. You can use it freely in both personal and commercial projects.
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