Simple WP MCP Adapter OAuth

Adds OAuth 2.1 authorization server support for WordPress MCP Adapter.

Motivation

WordPress MCP Adapter does not natively cover AI clients that require strict OAuth 2.1 flows.

This plugin fills that gap by turning the existing WordPress site into the OAuth authorization server for MCP access, reusing:

• the existing WordPress login (wp-login.php) for authentication
• a WordPress-hosted consent flow for authorization decisions

Requirements

• WordPress 6.8+
• PHP 7.4+
• OpenSSL extension
• WordPress MCP Adapter plugin

Features

• OAuth authorize endpoint with consent flow
• OAuth token endpoint
• PKCE support for Authorization Code flow (S256)
• Dynamic client registration endpoint
• OAuth discovery endpoint
• JWKS endpoint

Install (development)

1. Run composer install.
2. Activate the plugin in WordPress Admin.

How OAuthTransport is used

By default, this plugin registers SimpleWpMcpAdapterOAuth\OAuthTransport as the MCP transport by filtering mcp_adapter_default_server_config.

If you want to register a server with OAuthTransport explicitly, you can do:

add_action(
	'mcp_adapter_init',
	function ( $adapter ) {
		$adapter->create_server(
			'alpha-server',
			'alpha',
			'mcp',
			'Alpha MCP Server',
			'Central MCP server for Alpha',
			'1.0.0',
			array( \SimpleWpMcpAdapterOAuth\OAuthTransport::class ),
			null,
			null,
			array( 'alpha/get-posts' ),
			array(),
			array()
		);
	}
);

After activation, your MCP server exposes:

• OAuth protected resource metadata: /.well-known/oauth-protected-resource
• OAuth authorization server metadata: /.well-known/oauth-authorization-server
• OAuth token endpoint: /token

All OAuth endpoints

Assuming:

• Namespace: {namespace}
• MCP route: {server_route}
• REST prefix: /wp-json

Endpoints:

• GET /wp-json/{namespace}/{server_route} (MCP server endpoint)
• GET /wp-json/{namespace}/{server_route}/.well-known/oauth-protected-resource
• GET /wp-json/{namespace}/{server_route}/.well-known/oauth-authorization-server
• GET /wp-json/{namespace}/{server_route}/.well-known/jwks.json
• POST /wp-json/{namespace}/{server_route}/token
• POST /wp-json/{namespace}/{server_route}/register
• GET /wp-json/{namespace}/{server_route}/register/{client_id}
• PUT /wp-json/{namespace}/{server_route}/register/{client_id}
• DELETE /wp-json/{namespace}/{server_route}/register/{client_id}
• GET|POST /wp-admin/admin-post.php?action=simple_mcp_oauth_authorize