[Documentation] Add MCP README

Author: djalmaaraujo

mcp/README.md

@@ -0,0 +1,45 @@
+# ruby_ui-mcp
+
+Model Context Protocol (MCP) server for [Ruby UI](https://rubyui.com). Lets AI coding agents discover, inspect, and install Ruby UI components.
+
+Hosted endpoint: **https://rubyui.com/mcp**
+
+## Tools
+
+| Tool | Purpose |
+|------|---------|
+| `get_project_registries` | List available registries (always returns `ruby_ui`). |
+| `list_items_in_registries` | All components with descriptions. |
+| `search_items_in_registries` | Fuzzy search by name, description, or docs. |
+| `view_items_in_registries` | Full source + dependencies for given components. |
+| `get_item_examples_from_registries` | Code examples per component. |
+| `get_add_command_for_items` | Validated `rails g ruby_ui:component …` command. |
+| `get_audit_checklist` | Post-install verification checklist. |
+
+## Architecture
+
+- Rails engine gem, sibling of `gem/` and `docs/` in the monorepo.
+- Static `data/registry.json` built from `../gem/` by `exe/ruby-ui-mcp-build`, committed to the repo.
+- Mounted inside the `docs/` Rails app at `/mcp` via `RubyUI::MCP::Engine`.
+- HTTP transport via `mcp` ruby-sdk (`StreamableHTTPTransport`).
+- Read-only; component installs happen client-side via the Ruby UI generator.
+
+## Development
+
+```bash
+cd mcp
+bundle install
+bundle exec rake test
+```
+
+Rebuild the registry from the sibling gem:
+
+```bash
+bundle exec exe/ruby-ui-mcp-build
+```
+
+CI verifies the committed `data/registry.json` matches a fresh build (`mcp-registry-check` job).
+
+## Client setup
+
+See https://rubyui.com/docs/mcp for per-client install snippets (Claude Code, Cursor, Claude Desktop, Windsurf, VS Code, Zed).