Apps overview

MCP Apps let a tool point to a self-contained ui:// HTML resource. A compatible client host can open the view, deliver tool input and structured results, update host context, and allow controlled same-server tool calls. Normal text and structured tool output remain available as fallback for clients without Apps support.

The adapter registers and validates Apps declarations; it is not an Apps host. The client remains responsible for iframe sandboxing, CSP enforcement, permissions, user approvals, display modes, resizing, and audit logging.

• Quick Start registers a launch tool and resource.
• Configuration covers metadata, visibility, and security.
• Examples covers the vanilla and React Bun builds.