Borrowing it
Nothing to install: this file belongs to OlliMakarova/mcp-metro. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/OlliMakarova/mcp-metro/master/.claude/skills/mcp-app-create/SKILL.mdgit clone --depth 1 https://github.com/OlliMakarova/mcp-metroWrote 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.
[](https://agentmods.dev/skills/ollimakarova/mcp-metro/mcp-app-create)<a href="https://agentmods.dev/skills/ollimakarova/mcp-metro/mcp-app-create"><img src="https://agentmods.dev/badge/skills/ollimakarova/mcp-metro/mcp-app-create/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.
<a href="https://agentmods.dev/skills/ollimakarova/mcp-metro/mcp-app-create"><img src="https://agentmods.dev/badge/skills/ollimakarova/mcp-metro/mcp-app-create.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00077 | $0.02816 |
| Opus 5 | $0.00039 | $0.01408 |
| Sonnet 5 | $0.00015 | $0.00563 |
| Haiku 4.5 | $0.00008 | $0.00282 |
Grade A, and why
mcp-app-create 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 10d 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.
This is a copy
92% identical to mcp-app-create — 10 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.
How it starts
The opening of the file, as written. The whole thing — 239 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
The tool's _meta.ui.resourceUri references the resource's URI.
Host calls tool → Host renders resource UI → Server returns result → UI receives result.
Preferred pattern: reference the widget via
_meta.ui.resourceUri. This "Tool + separate Resource" form — the tool declares_meta.ui.resourceUriand the HTML is registered as its ownui://resource that the host fetches withresources/read— is the recommended way to ship a widget, and the only one this skill scaffolds. Prefer it over the embedded alternative, where the tool returns theui://resource inline in its resultcontent[]. The referenced form lets the host fetch and cache the static shell once, review its_meta.ui(CSP, permissions, domain) before rendering, and know the widget exists before the call — which is what enables app-only tools (visibility: ["app"]) and the "UI" badge / "Launch widget" button in the Agent Tester Inspector. Reserve the embedded form for quick, one-off, fully data-dependent widgets where those benefits don't matter.
Quick Start Decision Tree
Framework Selection
| Framework | @modelcontextprotocol/ext-apps 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,registerAppResourcefrom@modelcontextprotocol/ext-apps - Add tool registration with
_meta.ui.resourceUri - Add resource registration serving bundled HTML
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.
- 10d ago First seen · 239 lines · 77 tokens per session scan A 1014c3b1ab92
mcp-app-create is a skill published in the GitHub repository OlliMakarova/mcp-metro (0 stars, last pushed 1mo ago), licensed MIT. It adds 77 tokens to every session and 2,816 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. It is 92% identical to mcp-app-create, differing in 10 lines, and is treated as a copy.
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