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Lesson 7.4 · 4:40

What MCP is

Goal: Understand MCP as a standard plug that adds outside tools to any harness.

Try it

  1. Open OpenCode in your practice-app folder (with the browser tool from 6.2 still set up).
  2. Ask: List the tools you have from MCP servers. For each, say whether it only reads or can change something.
  3. Pick one tool that can change something and write one sentence on why you'd want to approve it yourself.

No code changes today. This lesson is about looking.

You're done when you have the tool list, each tool marked "reads" or "changes", and one sentence about a tool you'd keep on ask-first.

Recap

  • MCP is a standard plug between a harness and outside tools, like USB-C.
  • The host is the harness (OpenCode). An MCP server is a small program offering tools.
  • Plugging in doesn't make a tool safe. Read what it can change, and keep permissions on.

Next lesson (7.5): use a connected tool safely, reading, checking, approving a write, and reading back.