CLI Usage Guide

This guide covers how to use the MCP Adapter's CLI functionality for STDIO transport and development workflows.

Overview

The MCP Adapter includes WP-CLI commands that enable communication with MCP clients via standard input/output (STDIO) using the JSON-RPC 2.0 protocol. This is particularly useful for:

• Development and testing workflows
• Command-line automation and scripting
• IDE integrations and development tools

Available Commands

wp mcp-adapter serve

Serves an MCP server via STDIO transport for communication with MCP clients.

Syntax

wp mcp-adapter serve [--server=<server-id>] [--user=<id|login|email>]

Options

• --server=<server-id> - The ID of the MCP server to serve. If not specified, uses the first available server.
• --user=<id|login|email> - Run as a specific WordPress user for permission checks. Without this, runs as unauthenticated (limited capabilities).

Examples

# Serve the default MCP server as admin user
wp mcp-adapter serve --user=admin

# Serve a specific server as user with ID 1
wp mcp-adapter serve --server=my-mcp-server --user=1

# Serve without authentication (limited capabilities)
wp mcp-adapter serve --server=public-server

wp mcp-adapter list

Lists all available MCP servers and their configurations.

Syntax

wp mcp-adapter list [--format=<format>]

Options

• --format=<format> - Output format (table, json, csv, yaml). Default: table.

Examples

# List servers in table format
wp mcp-adapter list

# List servers in JSON format
wp mcp-adapter list --format=json

STDIO Transport Protocol

The STDIO transport uses JSON-RPC 2.0 protocol for communication:

Request Format

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/list",
  "params": {}
}

Response Format

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "tools": [...]
  }
}

Integration Examples

Using with MCP Clients

Configure MCP clients (Claude Desktop, Claude Code, VS Code, Cursor, etc.) to connect to your WordPress MCP servers. Many MCP clients can launch subprocess servers directly via STDIO; others need an HTTP proxy.

STDIO transport (local sites)

Many MCP clients can launch subprocess servers. Point the client's config at the wp binary:

{
  "mcpServers": {
    "wordpress": {
      "command": "wp",
      "args": [
        "--path=/path/to/your/wordpress/site",
        "mcp-adapter",
        "serve",
        // Change the server ID and user as needed
        "--server=mcp-adapter-default-server",
        "--user=admin"
      ]
    },
  }
}

HTTP transport via proxy

The @automattic/mcp-wordpress-remote proxy runs locally and translates STDIO-based MCP communication from AI clients into HTTP REST API calls that WordPress understands. Authentication uses WordPress Application Passwords.

{
  "mcpServers": {
    "wordpress": {
      "command": "npx",
      "args": [
        "-y",
        "@automattic/mcp-wordpress-remote@latest"
      ],
      "env": {
        // Update these to match your environment details
        "WP_API_URL": "http://your-site.test/wp-json/mcp/mcp-adapter-default-server",
        "LOG_FILE": "/path/to/logs/mcp-adapter.log",
        "WP_API_USERNAME": "your-username",
        "WP_API_PASSWORD": "your-application-password"
      }
    }
  }
}

For more information, see the @automattic/mcp-wordpress-remote package documentation.

Development Workflow

The CLI commands are particularly useful for development:

# Test your MCP server locally
wp mcp-adapter serve --user=admin --server=my-dev-server

# List available servers during development
wp mcp-adapter list --format=json | jq '.[].id'

# Test with different user permissions
wp mcp-adapter serve --user=editor --server=content-server

Authentication and Permissions

User Context

When using the --user option, the MCP server runs with that user's capabilities:

# Run as administrator (full access)
wp mcp-adapter serve --user=admin

# Run as editor (limited access)
wp mcp-adapter serve --user=editor

# Run as specific user ID
wp mcp-adapter serve --user=123

Permission Debugging

Use WP-CLI's --debug flag to see permission checks:

wp mcp-adapter serve --user=admin --debug

Error Handling

The CLI commands include comprehensive error handling:

Common Errors

Server Not Found

wp mcp-adapter serve --server=nonexistent
# Error: Server with ID  'nonexistent' not found.

User Not Found

wp mcp-adapter serve --user=baduser
# Error: Invalid user ID, email or login:'baduser'

No Servers Available

wp mcp-adapter serve
# Error: No MCP servers available. Make sure servers are registered via mcp_adapter_init.

Debug Output

Enable debug output for troubleshooting:

wp mcp-adapter serve --user=admin --debug

This will show:

• Server initialization process
• User authentication details
• Request/response flow
• Error details

Advanced Usage

Custom Server Selection

When multiple servers are available, specify which one to serve:

# List available servers
wp mcp-adapter list

# Serve specific server
wp mcp-adapter serve --server=content-management --user=admin

Environment-Specific Configurations

Use different configurations for different environments:

# Development
wp mcp-adapter serve --server=dev-server --user=admin

# Staging
wp mcp-adapter serve --server=staging-server --user=staging-user

# Production (limited access)
wp mcp-adapter serve --server=prod-server --user=api-user

Best Practices

Development

• Use --debug during development for detailed output
• Test with different user roles to verify permissions
• Use wp mcp-adapter list to verify server registration

Production

• Specify user explicitly for consistent permissions
• Use specific server IDs rather than defaults
• Implement proper error handling in client applications

Security

• Avoid running as admin user unless necessary
• Use least-privilege user accounts
• Validate server IDs to prevent unauthorized access

This CLI functionality provides a powerful interface for integrating WordPress MCP servers with development tools and automated workflows and MCP clients.