2.4 — MCP Server Integration

CCAR-F Domain 2 · Task 2.4

What You Need to Know

An MCP server extends Claude by connecting it to an external system (database, API, development tool, issue tracker).

The Scoping Hierarchy

Level	File	Scope
Project	.mcp.json (repo root)	Version-controlled, shared with whole team
User	~/.claude.json	Personal, not shared

All tools from all configured servers (project + user) are discovered at connection time and available simultaneously.

Environment Variable Expansion

.mcp.json supports ${VARIABLE_NAME} syntax so credentials stay out of version control:

{
  "env": {
    "GITHUB_TOKEN": "${GITHUB_TOKEN}",
    "DATABASE_URL": "${DATABASE_URL}"
  }
}

Also supports ${VAR:-default} fallback form.

MCP Resources

Resources expose a content catalogue to an agent upfront (issue lists, documentation hierarchies, database schemas). This reduces exploratory tool calls. Resources show agents what data is available; tools let them act on it.

The Build-vs-Use Decision

• Use community servers for standard integrations (Jira, GitHub, Slack, Linear, Notion).
• Build custom only for team-specific workflows, custom business logic, or proprietary internal systems with no community server.

Detailed MCP Tool Descriptions

When an MCP tool has a sparse description, the agent may prefer a built-in tool even when the MCP tool is more capable. Write detailed descriptions that explain capabilities and outputs.

Exam Traps

• Building a custom MCP server for a standard integration like Jira
• Putting team-wide MCP configuration in ~/.claude.json
• Pasting a token into .mcp.json
• Adding a system prompt rule or removing built-in tools to force use of an MCP tool