MCP Apps is the officially maintained protocol-extension repository from modelcontextprotocol, providing the spec, a multi-package SDK, and roughly 20 example servers so MCP tools can return interactive UIs rendered inline in compliant chat clients — it is not itself a single installable MCP server. Well suited to developers building rich in-chat UI experiences, but users should verify their target host's support level and the repo's actual license before adopting it.
Official repository from the Model Context Protocol project containing the specification and SDK for MCP Apps, an extension to core MCP that lets tools declare ui:// resources (HTML interfaces) so hosts (Claude, ChatGPT, VS Code, and other compliant clients) can render charts, forms, dashboards, and other interactive UIs inline in a sandboxed iframe, with bidirectional communication between the UI and host tools. The repo is not itself a single runnable MCP server — it bundles the protocol spec, a TypeScript SDK (core, React hooks, app-bridge, server helpers), four Agent Skills for scaffolding/migrating apps, and roughly 20 example servers (maps, 3D scenes, PDF viewers, QR codes, etc.). The README shows an Apache 2.0 license badge while the repo's catalog metadata records the license as NOASSERTION — this discrepancy should be verified before relying on licensing terms.
There is no single installable MCP server here — install the SDK with npm install -S @modelcontextprotocol/ext-apps to build your own app, or clone the repo and run npm install && npm start, then open http://localhost:8080/ to try all bundled examples against the included reference host, basic-host. Each Node.js example is also published individually as @modelcontextprotocol/server-<name> and can be added to a stdio-capable client (Claude Desktop, VS Code, etc.) with npx -y @modelcontextprotocol/server-<name> --stdio. Python examples (qr-server, say-server) are launched with uv run instead. If using an AI coding agent, the four bundled Agent Skills can also be installed via the Claude Code plugin marketplace to scaffold or migrate MCP Apps.