stable extension · S-039
MCP Apps
Return an interactive interface from an MCP tool for rendering inside a compatible host.
Markdown · JSON · Canonical source
- Revision
- 2026-01-26
- Maturity
- stable extension
- Authority
- MCP project
- Structure
- MCP extension, ui resource, and sandboxed frame
- Roles
- host, server, app
MCP Apps defines an interactive UI layer on top of MCP. The host discovers a declared UI resource, renders it in an isolated frame, and mediates communication with the tool and host.
Tool calling and app rendering remain separate catalog capabilities. Host listing, plan availability, developer-mode access, sandbox behavior, and extension revision should remain visible in the evidence.
Catalog mapping
Atomic capability rows
Absence here means the feature tree has not yet been published, not that the specification lacks the capability.
- MCP AppsRender an interactive interface returned by an MCP server inside the product.
Conformance boundary
Proposed tests
Definitions only. No fixture has been executed against a harness.
- T-APP-001ui resource discovery and sandbox render · optional