README

A powerful Symfony package to build a Model Context Protocol Server seamlessly

Overview

Symfony MCP Server is a powerful package designed to streamline the implementation of Model Context Protocol (MCP) servers in Symfony applications. This package utilizes Server-Sent Events (SSE) transport, providing a secure and controlled integration method.

Why SSE instead of STDIO?

While stdio is straightforward and widely used in MCP implementations, it has significant security implications for enterprise environments:

Security Risk: STDIO transport potentially exposes internal system details and API specifications
Data Protection: Organizations need to protect proprietary API endpoints and internal system architecture
Control: SSE offers better control over the communication channel between LLM clients and your application

By implementing the MCP server with SSE transport, enterprises can:

Expose only the necessary tools and resources while keeping proprietary API details private
Maintain control over authentication and authorization processes

Key benefits:

Seamless and rapid implementation of SSE in existing Symfony projects
Support for the latest Symfony and PHP versions
Efficient server communication and real-time data processing
Enhanced security for enterprise environments

Key Features

Real-time communication support through Server-Sent Events (SSE) integration
Implementation of tools and resources compliant with Model Context Protocol specifications
Adapter-based design architecture with Pub/Sub messaging pattern (starting with Redis, more adapters planned)
Simple routing and middleware configuration

Requirements

PHP >=8.2
Symfony >=7

Installation

Install the package via Composer:

composer require klapaudius/symfony-mcp-server

Create the configuration file config/packages/klp_mcp_server.yaml and paste into it:

klp_mcp_server:
    enabled: true
    server:
        name: 'Klp MCP Server'
        version: '0.1.0'
    default_path: 'mcp'
    ping:
        enable: false
        interval: 60
    middlewares:
        []
    server_provider: 'sse'
    sse_adapter: 'redis'
    adapters:
        redis:
            prefix: 'mcp_sse_'
            host: 'localhost'  # change it as needed
            ttl: 100
    tools:
        - KLP\KlpMcpServer\Services\ToolService\Examples\HelloWorldTool
        - KLP\KlpMcpServer\Services\ToolService\Examples\VersionCheckTool
    prompts: []
    resources: []

For more detailed explanations, you can open the default configuration file from that link.

Basic Usage

Creating and Adding Custom Tools

The package provides convenient Artisan commands to generate new tools:

php bin/console make:mcp-tool MyCustomTool

This command:

Handles various input formats (spaces, hyphens, mixed case)
Automatically converts the name to the proper case format
Creates a properly structured tool class in src/MCP/Tools
Offers to automatically register the tool in your configuration

You can also manually create and register tools in config/packages/klp_mcp_server.yaml:

use KLP\KlpMcpServer\Services\ToolService\ToolInterface;

class MyCustomTool implements ToolInterface
{
    // Tool implementation
}

Testing MCP Tools

The package includes a special command for testing your MCP tools without needing a real MCP client:

# Test a specific tool interactively
php bin/console mcp:test-tool MyCustomTool

# List all available tools
php bin/console mcp:test-tool --list

# Test with specific JSON input
php bin/console mcp:test-tool MyCustomTool --input='{"param":"value"}'

This helps you rapidly develop and debug tools by:

Showing the tool's input schema and validating inputs
Executing the tool with your provided input
Displaying formatted results or detailed error information
Supporting complex input types including objects and arrays

Visualizing MCP Tools with Inspector

You can also use the Model Context Protocol Inspector to visualize and test your MCP tools:

# Run the MCP Inspector without installation
npx @modelcontextprotocol/inspector node build/index.js

This will typically open a web interface at localhost:6274. To test your MCP server:

Warning: symfony server:start CANNOT be used with this package because it cannot handle multiple PHP connections simultaneously. Since MCP SSE requires processing multiple connections concurrently, you must use one of these alternatives:
- Nginx + PHP-FPM
- Apache + PHP-FPM
- Custom Docker setup
- Any web server that properly supports SSE streaming
In the Inspector interface, enter your Symfony server's MCP SSE URL (e.g., http://localhost:8000/mcp/sse)
Connect and explore available tools visually

The SSE URL follows the pattern: http://[your-web-server]/[default_path]/sse where default_path is defined in your config/packages/klp_mcp_server.yaml file.

Advanced Features

Pub/Sub Architecture with SSE Adapters

The package implements a publish/subscribe (pub/sub) messaging pattern through its adapter system:

Publisher (Server): When clients send requests to the /message endpoint, the server processes these requests and publishes responses through the configured adapter.
Message Broker (Adapter): The adapter (e.g., Redis) maintains message queues for each client, identified by unique client IDs. This provides a reliable asynchronous communication layer.
Subscriber (SSE Connection): Long-lived SSE connections subscribe to messages for their respective clients and deliver them in real-time.

This architecture enables:

Scalable real-time communication
Reliable message delivery even during temporary disconnections
Efficient handling of multiple concurrent client connections
Potential for distributed server deployments

Redis Adapter Configuration

The default Redis adapter can be configured as follows:

klp_mcp_server:
    sse_adapter: 'redis'
    adapters:
        redis:
            prefix: 'mcp_sse_'  # Prefix for Redis keys
            host: 'localhost'   # Change it as needed
            ttl: 100            # Message TTL in seconds

Credits

Boris AUBE and all contributors
Inspired by OP.GG/laravel-mcp-server

License

This project is distributed under the MIT license.

klapaudius / symfony-mcp-server

Maintainers

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