building-ui

building-ui is a skill for Claude Code, Codex from Intelligent-Internet/ii-agent. It costs 30 tokens per session (2,423 once invoked), scanned A, original, Apache-2.0.

A guide to building mobile app interfaces with Expo Router, a tool for making React Native apps and organizing their screens. It covers layouts, navigation, native controls, animations, media, storage, and visual effects.

In plain words
What is it for?
Use it when building Expo apps with routes, tabs, search, icons, forms, animations, camera or media features, local storage, gradients, or 3D graphics.
Why use it?
It gives developers patterns and instructions for creating consistent mobile screens without having to work out each Expo feature from scratch.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Needs its repository: it reads a path above its own folder, which exists only inside the repository. The line is import { Theme } from "../components/theme";.

Good fit Use it when building Expo apps with routes, tabs, search, icons, forms, animations, camera or media features, local storage, gradients, or 3D graphics.

Compare 6 skills from other repositories ↓
About the project

II-Agent is an open-source framework and AI agent for building applications, conducting research, and automating workflows from natural-language prompts. Developers, research teams, and enterprises use it to create mobile apps, websites, illustrated books, media, research outputs, and integrations with external services. The catalogue skills and instructions provide workflows and integrations for using II-Agent.

Intelligent-Internet/ii-agent · 3,382 stars · on GitHub · ii.inc

Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/Intelligent-Internet/ii-agent
agentmods
npx agentmods add skills/intelligent-internet/ii-agent/expo-building-ui

Made for: Claude Code, Codex.

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.

agentmods badge for building-ui

README.md
[![agentmods](https://agentmods.dev/badge/skills/intelligent-internet/ii-agent/expo-building-ui/github.svg)](https://agentmods.dev/skills/intelligent-internet/ii-agent/expo-building-ui)
Your own site
<a href="https://agentmods.dev/skills/intelligent-internet/ii-agent/expo-building-ui"><img src="https://agentmods.dev/badge/skills/intelligent-internet/ii-agent/expo-building-ui/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.

agentmods 80×15 button for building-ui

Your own site · 80×15
<a href="https://agentmods.dev/skills/intelligent-internet/ii-agent/expo-building-ui"><img src="https://agentmods.dev/badge/skills/intelligent-internet/ii-agent/expo-building-ui.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 30 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,423 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. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 3 findings, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium MCP Rug Pull · line 30
    npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.
    Fix: Pin the version: npx @scope/[email protected]
  • medium MCP Rug Pull · line 32
    npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.
    Fix: Pin the version: npx @scope/[email protected]
  • medium MCP Rug Pull · line 38
    npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.
    Fix: Pin the version: npx @scope/[email protected]
How audits are shown
Origin original No closer match found 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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00030 $0.02423
Opus 5 $0.00015 $0.01211
Sonnet 5 $0.00006 $0.00485
Haiku 4.5 $0.00003 $0.00242

Measured 11d ago against content hash 86ceb2608914, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

building-ui 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 11d 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.

src/ii_agent/agents/skills/builtin/expo-building-ui/SKILL.md · 315 lines

How it starts

The opening of the file, as written. The whole thing — 315 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Expo UI Guidelines

References

Consult these resources as needed:

  • ./references/route-structure.md -- Route file conventions, dynamic routes, query parameters, groups, and folder organization
  • ./references/tabs.md -- Native tab bar with NativeTabs, migration from JS tabs, iOS 26 features
  • ./references/icons.md -- SF Symbols with expo-symbols, common icon names, animations, and weights
  • ./references/controls.md -- Native iOS controls: Switch, Slider, SegmentedControl, DateTimePicker, Picker
  • ./references/visual-effects.md -- Blur effects with expo-blur and liquid glass with expo-glass-effect
  • ./references/animations.md -- Reanimated animations: entering, exiting, layout, scroll-driven, and gestures
  • ./references/search.md -- Search bar integration with headers, useSearch hook, and filtering patterns
  • ./references/gradients.md -- CSS gradients using experimental_backgroundImage (New Architecture only)
  • ./references/media.md -- Media handling for Expo Router including camera, audio, video, and file saving
  • ./references/storage.md -- Data storage patterns including SQLite, AsyncStorage, and SecureStore
  • ./references/webgpu-three.md -- 3D graphics, games, and GPU-powered visualizations with WebGPU and Three.js

Running the App

CRITICAL: Always try Expo Go first before creating custom builds.

Most Expo apps work in Expo Go without any custom native code. Before running npx expo run:ios or npx expo run:android:

  1. Start with Expo Go: Run npx expo start and scan the QR code with Expo Go
  2. Check if features work: Test your app thoroughly in Expo Go
  3. Only create custom builds when required - see below

When Custom Builds Are Required

You need npx expo run:ios/android or eas build ONLY when using:

  • Local Expo modules (custom native code in modules/)
  • Apple targets (widgets, app clips, extensions via @bacons/apple-targets)
  • Third-party native modules not included in Expo Go
  • Custom native configuration that can't be expressed in app.json

Read the full file on GitHub · 315 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.

  1. 11d ago First seen · 315 lines · 30 tokens per session scan A 86ceb2608914

Subscribe to this mod's changes

building-ui is a skill published in the GitHub repository Intelligent-Internet/ii-agent (3,382 stars, last pushed 25d ago), licensed Apache-2.0. It adds 30 tokens to every session and 2,423 once invoked, about $0.0002 per session on Opus 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 2026-08-30.

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