MCP Apps Explained
MCP Apps is an official extension that lets an MCP tool return an interactive user interface alongside normal tool output. Compatible hosts can render forms, dashboards, charts, pickers, and multi-step interactions directly in the conversation.
Tool + UI resource
The core pattern combines an MCP tool with a UI resource. The host renders the view in a sandboxed frame and mediates communication between the app and MCP capabilities.
Progressive enhancement
A tool should still provide useful standard output when a host cannot render the app UI. That keeps the server usable across clients with different extension support.
Security model
Interactive UI adds browser-like risks. Use sandboxing, content/security policy, explicit tool-call mediation, and do not assume app code deserves unrestricted host access.