MCP Integration

Source: src/services/mcp/ (24 files)

Overview

The Model Context Protocol (MCP) is an open standard for AI tool interoperability. Claude Code implements a full MCP client that connects to external MCP servers to extend its tool capabilities.

Architecture

Key Files

File	Purpose
`client.ts`	Core MCP client implementation
`config.ts`	Server configuration loading
`auth.ts`	Authentication handling
`channelPermissions.ts`	Permission management for MCP tools
`elicitationHandler.ts`	Interactive prompts from MCP servers
`InProcessTransport.ts`	In-process server transport
`SdkControlTransport.ts`	SDK-based transport

Server Configuration

MCP servers are defined in settings with:


{
  "mcpServers": {
    "server-name": {
      "command": "npx",
      "args": ["-y", "@org/mcp-server"],
      "env": { "API_KEY": "..." }
    }
  }
}

Capabilities

MCP servers can provide:

Tools — Executable functions with JSON Schema parameters
Resources — Readable data sources (files, APIs, databases)
Prompts — Pre-defined prompt templates for common tasks

Connection Lifecycle

Discovery — Load server configs from settings
Launch — Start server processes (or connect to running servers)
Handshake — Exchange capabilities via MCP protocol
Registration — Register server tools as available Claude Code tools
Execution — Forward tool calls to servers, return results
Cleanup — Gracefully shut down servers on exit

Deep Dive

Client Architecture — MCP client internals, transport abstractions (stdio, SSE, in-process)
Server Lifecycle — Discovery, launch, handshake, capability exchange, and cleanup
Tool Registration — How MCP server tools become Claude Code tools, schema mapping, and permission integration