What Are the Components and Interaction Flow of MCP in AI Agents? A Complete Guide

Standard Answer

MCP (Model Context Protocol) is a standardized interface that enables AI applications to connect to external data sources and tools, acting like a "Type‑C" port for AI agents. It allows connections to local files, databases, search engines, calculators, workflows, or specialized prompts to retrieve context and perform tasks.

Extended Q&A

1. Difference between MCP and Function Calling

Function calling is an internal capability of large language models (LLMs) and its response format varies across models such as ChatGPT and Claude. MCP, by contrast, is an external, model‑agnostic protocol that any AI application can adopt, enabling multiple applications to use the same MCP server.

2. How MCP Ensures Security

MCP itself does not provide protocol‑level security; developers must apply application‑layer safeguards such as sandbox isolation, the principle of least privilege, manual authorization, and comprehensive security documentation.

MCP Detailed Analysis

1. Architecture Design

MCP follows a client‑server model. The MCP Host (e.g., OpenClaw, Doubao) manages MCP Clients, which maintain connections to one or more MCP Servers that supply context information.

MCP Host: The AI application that oversees all MCP Clients.

MCP Client: Maintains the connection to an MCP Server and fetches context for the Host.

MCP Server: Provides context services to Clients; it can run locally or remotely.

The interaction flow is illustrated in the diagram below.

2. Three Basic Types

MCP supports three resource types, each with corresponding methods:

Tools: Executable functions such as file operations or database queries.

Resources: Contextual data like file contents or database records.

Prompts: Reusable prompt templates, including system prompts and few‑shot examples.

Clients can invoke methods like /list to discover available server types before proceeding with further tasks.

3. Transport Protocols

Communication between MCP Client and Server uses JSON‑RPC 2.0 over two possible transports:

Standard Input/Output (Stdio): Direct process communication on the same machine, offering optimal performance with no network overhead.

Streamable HTTP: HTTP POST messages, optionally using Server‑Sent Events (SSE) for streaming. Supports Bearer Token, API Key, and custom header authentication, suitable for remote server interactions.

Note: In March 2025 MCP transitioned from an HTTP + SSE approach to the Streamable HTTP protocol; the reasons for this change are not detailed here.