Introduction to MCP

What is the Model Context Protocol?

The Model Context Protocol (MCP) is an open-source standard developed by Anthropic for connecting AI applications to external systems. It provides a unified way for Large Language Models (LLMs) and AI agents to:

• Access external data sources
• Execute tools and functions
• Use predefined workflows and prompts

The Problem MCP Solves

Before MCP, every AI integration required custom code:

Without MCP:
AI App → Custom Notion Code → Notion API
AI App → Custom Slack Code → Slack API
AI App → Custom Database Code → Database
AI App → Custom GitHub Code → GitHub API

This approach has significant drawbacks:

• Duplication: Each AI app reimplements the same integrations
• Inconsistency: Different apps handle the same APIs differently
• Maintenance burden: Updates to APIs require changes everywhere
• Security risks: Multiple implementations mean multiple attack surfaces

The MCP Solution

MCP standardizes the connection layer:

With MCP:
AI App → MCP Client → MCP Server (Notion) → Notion API
                   → MCP Server (Slack) → Slack API
                   → MCP Server (Database) → Database
                   → MCP Server (GitHub) → GitHub API

Benefits:

• Write once, use everywhere: MCP servers work with any MCP-compatible client
• Consistent interface: All integrations follow the same patterns
• Centralized security: Security handled at the protocol level
• Growing ecosystem: Community-built servers for popular services

Key Concepts

Three Primitives

MCP defines three core primitives for AI interaction:

Primitive	Control	Purpose	Example
Tools	Model-controlled	Execute actions	Search database, send email
Resources	Application-controlled	Provide context	File contents, API data
Prompts	User-controlled	Workflow templates	Code review, summarization

Communication Model

MCP uses JSON-RPC 2.0 over two transport types:

1. stdio - For local processes (command-line tools)
2. Streamable HTTP - For remote servers (web services)

sequenceDiagram
    participant Host as Rea (Host)
    participant Client as MCP Client
    participant Server as MCP Server

    Host->>Client: Initialize
    Client->>Server: initialize request
    Server-->>Client: capabilities response
    Client-->>Host: Ready

    Host->>Client: List tools
    Client->>Server: tools/list
    Server-->>Client: Available tools
    Client-->>Host: Tool definitions

    Host->>Client: Call tool
    Client->>Server: tools/call
    Server-->>Client: Tool result
    Client-->>Host: Result

MCP in the Rea Context

For Rea to support MCP, the platform needs to act as an MCP Host with MCP Client capabilities:

Current Rea Architecture

User → Rea UI → Rea Backend (Laravel/PHP) → AI Agents → ?

Target Architecture with MCP

User → Rea UI → Rea Backend → AI Agents → MCP Client → MCP Servers
                                              ↓
                                         Notion, Slack,
                                         Database, etc.

Implementation Requirements

1. MCP Client in PHP - Protocol implementation for connecting to servers
2. Server Management - Configuration and lifecycle for multiple MCP servers
3. Agent Integration - Exposing MCP tools to Rea's AI agents
4. Security Layer - Authentication and authorization for server connections

What's Next?

Now that you understand what MCP is, proceed to:

• Architecture Overview - Detailed technical architecture
• Quick Start - Get MCP running in Rea
• Notion Tutorial - Complete working example

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Official Documentation

For the complete MCP specification, visit modelcontextprotocol.io