Plug in your data

You have Claude Code (Chapter 06). You have a skill that encodes your organizational knowledge (Chapter 04). Now you connect your actual data.

MCP servers connect to Claude Code with one command. From your project directory:

claude mcp add quickbooks --env QB_ACCESS_TOKEN=... --env QB_REALM_ID=... \
  -- npx -y qb-mcp-server

That registers the server for you personally. Add --scope project and the config is written to a .mcp.json file at the project root instead — check it into git and everyone on the team gets the same connection:

{
  "mcpServers": {
    "quickbooks": {
      "command": "npx",
      "args": ["-y", "qb-mcp-server"],
      "env": {
        "QB_ACCESS_TOKEN": "${QB_ACCESS_TOKEN}",
        "QB_REALM_ID": "${QB_REALM_ID}"
      }
    }
  }
}

Start Claude Code. The MCP server runs as a child process. Claude can now call its tools.

Verify it works — ask Claude: “What MCP tools do you have access to?” It will list the available tools from the connected server. Then ask a real question.

Cornwall Market: Sarah adds the QuickBooks MCP server and restarts Claude Code. She asks, “Show me all invoices over 30 days overdue.” For the first time, she is querying her accounting system through natural language instead of navigating menus and pulling reports. Claude returns a list — three invoices from Pacific Foods, one from a specialty supplier. She has been meaning to follow up on those.

The moment it comes together

This is the moment the book has been building toward. You have two things: a skill that knows how to do the work (categorization rules, vendor mappings, exception flags from Chapter 04) and an MCP connection that provides the actual data (live transactions, real invoices, current account balances from the connection you just made).

Put them together: “Categorize last week’s uncategorized transactions using our rules.”

Claude reads your categorization skill. It queries QuickBooks via MCP for last week’s transactions. It applies the vendor rules — Chen’s Produce items go to 5100, Pacific Foods items get split across departments, cleaning supplies go to 6100 not Cost of Goods. It flags the one Pacific Foods line item over $500 for review. It produces a categorized report.

This is Skills + MCP. Knowledge plus data. The skill without MCP knows rules but cannot see transactions. MCP without the skill can pull data but does not know your categorization logic. Together, they do what previously required a human with six months of experience at Cornwall Market.

Check your understanding

Answer in your own words — write it down before opening the key. Your tutor grades against the criteria and generates fresh variants on retries.

Q1. “Categorize last week’s uncategorized transactions using our rules.” Explain what the skill contributes, what MCP contributes, and why neither alone can complete this task.

Q2. What does adding —scope project to claude mcp add change, and why does that matter for a team rather than an individual?

Next: Build Your Own MCP Server