MCP Apps Widgets (SEP-1865)

An MCP tool can return more than JSON. With MCP Apps, a tool advertises a predeclared HTML "view" that Apps-capable hosts (e.g. Claude Desktop) render in a sandboxed iframe and drive over JSON-RPC. The tool still runs server-side as the calling identity under your access control; the view renders whatever the tool returned and can trigger follow-up tool calls through the host.

This skill builds on top of an existing MCP server (see raisindb-mcp-servers). Widgets are ordinary built HTML files shipped as raisin:Asset content — there is no widget node type.

MANDATORY: After creating or modifying any .yaml / .node.yaml file in package/, run npm run validate.

How the pieces fit