OAuth 2.1 Resource Server for MCP Servers

Security Requirement

MCP servers MUST be capable of acting as an OAuth 2.1 resource server, and this MUST be their default behavior. The server should not operate without authentication unless explicitly opted out by the deployer.

What "Resource Server" Means

As an OAuth 2.1 resource server, the MCP server:

• Accepts and validates OAuth 2.1 access tokens on every request
• Rejects requests without a valid token (401 Unauthorized)
• Enforces scopes from the token against the requested operation
• Publishes its Protected Resource Metadata for client discovery (see mcp_server/protected-resource-metadata)

Default Behavior