Descriptions:
Alpha Stack walks through building a custom plugin for Claude Code—Anthropic’s agentic coding environment—using the Model Context Protocol (MCP). The tutorial is grounded in a practical example: a visual annotation tool that lets users draw directly on a webpage, circle interface elements, and send the annotated screenshot as context into Claude, eliminating the need for manual screenshotting and typed descriptions when requesting UI changes.
The plugin architecture is broken into three layers. Slash commands are YAML-formatted markdown files that serve as Claude’s step-by-step instructions—the ‘brain’ of the plugin that defines what happens when a command is invoked. The MCP server is a configuration layer that registers available tools and maps their names to underlying implementation functions. App logic contains the actual code: browser automation, screenshot capture, microphone access, database queries, or any other functionality the plugin needs. The video shows the complete recommended file structure and how these three components interact at runtime.
The presenter also covers the Claude Code plugin marketplace, which supports installation directly from GitHub repositories or via zip upload, and notes that Anthropic ships several official plugins—including a multi-agent code review plugin—using the same architecture. A downloadable scaffold template (available at alphastack.fund/build-cloud-plugin) is provided as a starting point; the tutorial then shows Claude itself being used to flesh out the template into a working plugin, illustrating a self-referential build loop where the tool helps construct its own extension. The result is a reusable pattern applicable to any integration—cameras, microphones, databases, or external APIs.
📺 Source: Alpha Stack · Published February 12, 2026
🏷️ Format: Hands On Build
