What is Create MCP App?

A development guide for building MCP Apps: interactive web interfaces that run inside hosts such as Claude Desktop and connect to an MCP tool. It explains how the tool, its data, and the HTML interface fit together.

Use it to scaffold an MCP App, add a UI to an existing MCP server, register the interface, or choose an approach for React or plain JavaScript.

It removes the guesswork around linking an MCP tool to a user interface and making that interface work inside an MCP-enabled host.

How elbruno/mcpapp-colorpicker configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to elbruno/mcpapp-colorpicker. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/elbruno/mcpapp-colorpicker/master/.claude/skills/create-mcp-app/SKILL.md

Clone the repo

git clone --depth 1 https://github.com/elbruno/mcpapp-colorpicker

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/elbruno/mcpapp-colorpicker/create-mcp-app/github.svg)](https://agentmods.dev/skills/elbruno/mcpapp-colorpicker/create-mcp-app)

Your own site

<a href="https://agentmods.dev/skills/elbruno/mcpapp-colorpicker/create-mcp-app"><img src="https://agentmods.dev/badge/skills/elbruno/mcpapp-colorpicker/create-mcp-app/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/elbruno/mcpapp-colorpicker/create-mcp-app"><img src="https://agentmods.dev/badge/skills/elbruno/mcpapp-colorpicker/create-mcp-app.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 76 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 2,862 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin 92% copy Near-identical to another mod in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00076	$0.02862
Opus 5.5	$0.00030	$0.01145
Sonnet 5.5	$0.00015	$0.00572
Haiku 4.5	$0.00008	$0.00286

Measured 2mo ago against content hash 61eb20c068ce, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

Create MCP App scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

92% identical to create-mcp-app — 6 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.claude/skills/create-mcp-app/SKILL.md · 343 lines

How it starts

The opening of the file, as written. The whole thing — 343 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Create MCP App

Build interactive UIs that run inside MCP-enabled hosts like Claude Desktop. An MCP App combines an MCP tool with an HTML resource to display rich, interactive content.

Core Concept: Tool + Resource

Every MCP App requires two parts linked together:

Tool - Called by the LLM/host, returns data
Resource - Serves the bundled HTML UI that displays the data
Link - The tool's _meta.ui.resourceUri references the resource

Host calls tool → Server returns result → Host renders resource UI → UI receives result

Quick Start Decision Tree

Framework Selection

Framework	SDK Support	Best For
React	`useApp` hook provided	Teams familiar with React
Vanilla JS	Manual lifecycle	Simple apps, no build complexity
Vue/Svelte/Preact/Solid	Manual lifecycle	Framework preference

Project Context

Adding to existing MCP server:

Import registerAppTool, registerAppResource from SDK
Add tool registration with _meta.ui.resourceUri
Add resource registration serving bundled HTML

Creating new MCP server:

Set up server with transport (stdio or HTTP)
Register tools and resources
Configure build system with vite-plugin-singlefile

Getting Reference Code

Clone the SDK repository for working examples and API documentation:

git clone --branch "v$(npm view @modelcontextprotocol/ext-apps version)" --depth 1 https://github.com/modelcontextprotocol/ext-apps.git /tmp/mcp-ext-apps

Framework Templates

Learn and adapt from /tmp/mcp-ext-apps/examples/basic-server-{framework}/:

Template	Key Files
`basic-server-vanillajs/`	`server.ts`, `src/mcp-app.ts`, `mcp-app.html`
`basic-server-react/`	`server.ts`, `src/mcp-app.tsx` (uses `useApp` hook)
`basic-server-vue/`	`server.ts`, `src/App.vue`
`basic-server-svelte/`	`server.ts`, `src/App.svelte`
`basic-server-preact/`	`server.ts`, `src/mcp-app.tsx`
`basic-server-solid/`	`server.ts`, `src/mcp-app.tsx`

Read the full file on GitHub · 343 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

2mo ago First seen · 343 lines · 76 tokens per session scan A 61eb20c068ce

Subscribe to this mod's changes

Create MCP App is a skill published in the GitHub repository elbruno/mcpapp-colorpicker (13 stars, last pushed 7mo ago), licensed MIT. It adds 76 tokens to every session and 2,862 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 92% identical to create-mcp-app, differing in 6 lines, and is treated as a copy.

Building agents color-picker dotnet mcp mcp-app model-context-protocol

Create MCP App next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
Create MCP Appelbruno/mcpapp-colorpicker	Skill	13	7mo ago	MIT	A	76	Claude Code
collatticeMrBildo/collattice	Skill	8	10d ago	MIT	A	111	Claude Code, Codex
wpfvisualtreemcpfaze79/WPFVisualTreeMcp	Skill	21	11d ago	MIT	A	85	Claude Code, Codex
publish-releaseByggarepop/dotnet-mcp-orchestrator	Skill	2	17d ago	MIT	A	63	Claude Code, Codex
console-logIvanMurzak/MCP-Plugin-dotnet	Skill	21	yesterday	Apache-2.0	B	10	Claude Code, Codex
home-memory-documentationimpactjo/home-memory	Skill	77	13d ago	AGPL-3.0	A	112	Claude Code, Codex
release-notesByggarepop/dotnet-mcp-orchestrator	Skill	2	17d ago	MIT	A	39	Claude Code, Codex

mcpapp-colorpicker: Skill for Claude Code