UI5con 2026 Apps

Five runnable samples for learning how MCP tools can return deterministic, interactive UIs. The examples progress from plain HTML to UI5 Web Components, UI Integration Cards, a UI5 linter workflow, and host-orchestrated SAP transport data.

This repository contains the reusable sample code and learning material. Speaker notes, presentation files, editor-specific MCP configuration, generated output, helper scripts, and the original test suite are intentionally not part of this publication copy.

What an MCP App Adds

An ordinary MCP tool can return text and structured data. MCP Apps adds a prebuilt web UI that the host renders in a sandboxed iframe:

user asks for something
  -> model chooses an MCP tool
  -> server returns content + structuredContent
  -> tool metadata points to a ui:// resource
  -> host loads the prebuilt UI
  -> host bridge delivers the tool result to the iframe
  -> app renders structuredContent and may call another tool

The model chooses and connects tools; it does not generate the interface for each request. That separation keeps the UI predictable and lets non-UI hosts fall back to content.

Learning Path

Step	Package	Main tool	What it demonstrates
00	00-html-time	show_time	Smallest complete MCP App and an app-to-server callback.
01	01-ui5-webc-project-overview	show_ui5_project_overview	UI5 Web Components, host theme synchronization, and structured rendering.
02	02-ui5-card-project-overview	show_ui5_project_cards	Declarative Object and List UI Integration Cards.
03	03-ui5-lint-findings	show_ui5_lint_findings	Live developer tooling, server composition, callbacks, and a narrow file write.
04	04-arc1-transport	show_arc1_transport_list, show_arc1_transport	Host-orchestrated ARC-1 data and confirmation-gated SAP actions.

New to MCP or MCP Apps? Read LEARNING.md first, then work through the package READMEs in numeric order.

Prerequisites

• Node.js 22 and npm.
• An MCP host that supports MCP Apps, such as Cursor, Claude Desktop, or MCPJam.
• Network access for installing npm dependencies.
• Sample 03 additionally launches @ui5/mcp-server with npx and can use a local ui5lint fallback.
• Sample 04 needs a separately configured ARC-1 server for live SAP data. Its demo-data/ directory provides an explicitly labelled offline rehearsal fallback.

Install and Build

git clone https://github.com/marianfoo/UI5con_2026_MCPApps.git
cd UI5con_2026_MCPApps
npm ci
npm run build

The build has two outputs:

• Vite bundles every iframe app into a single packages/<sample>/app/dist/index.html.
• TypeScript compiles the MCP servers into dist/.

Rebuild after changing app or server source. Generated build output is ignored by Git.

Connect an MCP Host

Stdio: all samples

Use the root aggregator when exploring the repository:

command: node
args: /absolute/path/to/UI5con_2026_MCPApps/dist/src/stdio.js

The exact configuration screen differs by host. This repository intentionally does not ship an mcp.json, because absolute paths and local server credentials are machine-specific.

For a focused demo, expose only one sample by using its compiled entrypoint:

Sample	Command after npm run build
00	npm run start:stdio:00
01	npm run start:stdio:01
02	npm run start:stdio:02
03	npm run start:stdio:03
04	npm run start:stdio:04

When the host starts the process itself, configure node with the corresponding absolute dist/packages/<sample>/src/stdio.js path instead of running the npm command manually.

Streamable HTTP

Start the aggregate server:

npm run start

Then connect an HTTP-capable client to:

http://127.0.0.1:3000/mcp

Each package also has a standalone HTTP command from npm run start:00 through npm run start:04; their ports are 3010 through 3014.

First Prompts to Try

Call show_time.

Call show_ui5_project_overview.

Call show_ui5_project_cards.

Call show_ui5_lint_findings.

Sample 04 needs ARC-1 data first; its README contains the complete safe orchestration prompt.

Verify the Publication Copy

The essential local verification is:

npm ci
npm run build

For MCP Apps protocol conformance, start the aggregate HTTP server in one terminal and run the MCPJam check in another:

npm run start
npm run test:mcpjam

Conformance verifies protocol behavior, but it cannot guarantee identical rendering or CSP behavior in every host. Test the samples in the hosts you intend to support.

Repository Structure

packages/<sample>/
  README.md             sample concepts, flow, setup, and experiments
  src/register.ts       tools, schemas, ui:// resource, and result builder
  src/<domain>.ts       types, normalization, fixtures, or manifests
  src/server.ts         standalone Streamable HTTP entrypoint
  src/stdio.ts          standalone stdio entrypoint
  app/index.html        fixed iframe document
  app/src/main.ts       MCP Apps bridge and rendering logic
  app/src/styles.css    app-specific presentation

src/mcp-host.ts         shared server and resource plumbing
src/register-all.ts     aggregate tool registration
src/server.ts           aggregate HTTP server
src/stdio.ts            aggregate stdio server

Security and Portability Rules

• Treat structuredContent as a typed application contract, not generated markup.
• Validate every server tool input, including calls originating from your own iframe.
• Keep credentials and system connections on the server that owns them.
• Preserve useful content for hosts without MCP Apps support.
• Request only the CSP domains and iframe permissions a UI actually requires.
• Require explicit confirmation for consequential writes.
• Re-read authoritative data after a write rather than trusting optimistic UI state.
• Test strict and permissive hosts separately; MCP compatibility does not make their browser sandbox policies identical.

Technology

• @modelcontextprotocol/ext-apps
• @modelcontextprotocol/sdk
• UI5 Web Components
• UI Integration Cards
• UI5 MCP Server