MCP Tool

Source: src/tools/MCPTool/ and src/services/mcp/

Overview

The MCP Tool bridges Claude Code with external tool servers via the Model Context Protocol (MCP). This enables third-party tools and services to be used as native Claude Code tools.

How It Works

MCP servers are configured by the user (in settings or CLAUDE.md)
On startup, Claude Code connects to configured MCP servers
Each server’s tools are registered as available tools
When the AI calls an MCP tool, the request is forwarded to the server
The server’s response is returned as the tool result

MCP Server Configuration

MCP servers can be configured in:

~/.claude/settings.json — Global MCP servers
Project .claude/settings.json — Project-specific servers
CLAUDE.md — Inline MCP server definitions

Tool Naming

MCP tools are namespaced with their server name:


mcp__<server-name>__<tool-name>

For example: mcp__github__create_issue

Transport Types

The MCP client supports multiple transport mechanisms:

stdio — Communication via standard input/output
SSE — Server-Sent Events over HTTP
In-process — Direct function calls (for built-in MCP servers)

Authentication

MCP server authentication is handled via src/services/mcp/auth.ts, supporting:

API key-based auth
OAuth flows
Custom authentication schemes

Resources and Prompts

Beyond tools, MCP servers can also provide:

Resources — Data that can be read (files, databases, APIs)
Prompts — Pre-defined prompt templates