Borrowing it
Nothing to install: this file belongs to Cyruskraad/codex-claude-mcp. 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/Cyruskraad/codex-claude-mcp/main/.agents/skills/building-mcp-apps/SKILL.mdgit clone --depth 1 https://github.com/Cyruskraad/codex-claude-mcpWrote 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/cyruskraad/codex-claude-mcp/building-mcp-apps)<a href="https://agentmods.dev/skills/cyruskraad/codex-claude-mcp/building-mcp-apps"><img src="https://agentmods.dev/badge/skills/cyruskraad/codex-claude-mcp/building-mcp-apps/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/cyruskraad/codex-claude-mcp/building-mcp-apps"><img src="https://agentmods.dev/badge/skills/cyruskraad/codex-claude-mcp/building-mcp-apps.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 | $0.00033 | $0.00407 |
| Opus 5.5 | $0.00013 | $0.00163 |
| Sonnet 5.5 | $0.00007 | $0.00081 |
| Haiku 4.5 | $0.00003 | $0.00041 |
Grade A, and why
building-mcp-apps 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.
What it actually says
building-mcp-apps
Deliver an MCP App whose visual interaction earns its place and preserves useful model-visible fallback.
Use when
- Build an MCP App or widget.
- Add a host-visible interactive workflow.
Do not use when
- Do not use when concise text fully serves the user.
- Do not use for headless server work with no UI outcome.
Required inputs
- Target user and explicit UI benefit.
- Primary interaction and states.
- Model-visible result and text fallback.
Workflow
Read and follow the canonical playbook references/build-an-mcp-app.md at ../noodle-seed/references/build-an-mcp-app.md. It owns the workflow; do not recreate it here or load the command catalog speculatively.
Load references/experience-design.md at ../noodle-seed/references/experience-design.md only when the playbook or observed evidence names that concern.
Load references/widgets-and-apps.md at ../noodle-seed/references/widgets-and-apps.md only when the playbook or observed evidence names that concern.
Verification evidence
The App passes validation, local smoke, app checks, and the requested preview or host evidence level.
Recovery paths
Distinguish data-contract, widget-runtime, rendering, host, and deployment failures.
Stop conditions
Stop before deployment or publication unless that distinct outcome was requested.
Handoff contract
Pass the selected outcome, explicit target, changed files, commands run, passing evidence, first unproven evidence layer, sanitized failure, remaining authority, and exact next action. The receiving skill continues from that layer; do not restart discovery or discard prior proof.
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 · 49 lines · 33 tokens per session scan A 2dc299767f1f
building-mcp-apps is a skill published in the GitHub repository Cyruskraad/codex-claude-mcp (0 stars, last pushed 2mo ago), licensed MIT. It adds 33 tokens to every session and 407 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
building-mcp-apps compared with skills from other repositories
| Mod | Type | Stars | Last push | Licence | Scan | Tokens | Works with |
|---|---|---|---|---|---|---|---|
| building-mcp-appsCyruskraad/codex-claude-mcp | Skill | 0 | 2mo ago | MIT | A | 33 | Claude Code, Codex |
| imagegenopenai/codex | Skill | 133k | yesterday | Apache-2.0 | A | 113 | Codex |
| playwright-climicrosoft/playwright | Skill | 99k | yesterday | Apache-2.0 | A | 19 | Claude Code |
| local-ai-agentsmicrosoft/ai-agents-for-beginners | Skill | 79k | 4d ago | MIT | A | 200 | Claude Code, Codex |
| systematic-debuggingobra/superpowers | Skill | 313k | 3d ago | MIT | A | 21 | Claude Code |
| next-cache-components-adoptionvercel/next.js | Skill | 143k | yesterday | MIT | A | 95 | Claude Code |
| next-partial-prefetching-adoptionvercel/next.js | Skill | 143k | yesterday | MIT | A | 103 | Claude Code |