---
title: "Protocol Overview"
description: "Learn about the core concepts and architecture of the Model Context Protocol (MCP)"
---

The Model Context Protocol (MCP) is a standardized protocol that enables AI applications to securely access external data sources and tools. MCP follows a client-server architecture where AI applications act as clients that can connect to one or more MCP servers.

## Key features

<CardGroup cols={2}>
    <Card title="Flexible integration" icon="puzzle-piece">
        Connect AI models to any data source or tool through a unified protocol
    </Card>
    <Card title="Secure access" icon="shield-check">
        Control what data and capabilities are exposed to AI systems
    </Card>
    <Card title="Composable design" icon="cubes">
        Combine multiple servers together for enhanced functionality
    </Card>
    <Card title="Standard interface" icon="code">
        Build integrations that work consistently across AI applications
    </Card>
</CardGroup>

# Core concepts

MCP defines several key primitives that form the foundation of the protocol:

<CardGroup cols={2}>
  <Card title="Resources" icon="book">
    Data that can be loaded as context for the AI model. Resources have URIs and can contain text or binary data.
  </Card>
  <Card title="Tools" icon="screwdriver-wrench">
    Functions that the AI can invoke to perform actions, like writing files or calling APIs.
  </Card>
  <Card title="Prompts" icon="message">
    Pre-defined prompt templates that help guide AI interactions in specific ways.
  </Card>
  <Card title="Sampling" icon="rotate">
    Allows servers to request completions from the AI model through the client.
  </Card>
</CardGroup>

# Protocol flow

## Connection and initialization 

When a client connects to an MCP server, they go through the following initialization sequence:

<Steps>
  <Step title="Client connects">
    The client establishes a connection to the server using one of the supported transports.
  </Step>
  <Step title="Initialize request">
    The client sends an initialize request containing its capabilities and protocol version.
  </Step>
  <Step title="Server response">
    The server responds with its own capabilities and supported protocol version.
  </Step>
  <Step title="Initialized notification">
    The client sends an initialized notification to indicate setup is complete.
  </Step>
</Steps>

After initialization, the client can begin using the server's resources, tools, and other capabilities.

## Transport options

MCP supports multiple transport mechanisms for client-server communication:

<AccordionGroup>
  <Accordion title="Standard input/output (stdio)">
    - Server process reads from stdin and writes to stdout
    - Messages are newline-terminated JSON
    - Client manages server process lifetime
    - State is lost when process exits
  </Accordion>
  
  <Accordion title="WebSocket">
    - Bidirectional communication over WebSocket protocol
    - Client and server negotiate using 'mcp' subprotocol
    - Can connect to remote servers
    - State persists until disconnect
  </Accordion>
  
  <Accordion title="Server-Sent Events (SSE)">
    - Server pushes messages via SSE
    - Client sends messages via HTTP POST
    - Supports cross-origin restrictions
    - State persists until SSE connection closes
  </Accordion>
</AccordionGroup>