gem-designer

A UI and UX design agent that creates layouts, themes, colour schemes, and design systems, then checks visual structure, responsive behaviour, and accessibility.

In plain words
What is it for?
Use it to design or review interfaces, create themes and design systems, assess responsive layouts, and check visual hierarchy and accessibility. It can create designs but only validates existing work read-only.
Why use it?
It helps turn interface requirements into consistent designs and spot usability or accessibility problems before release.

Agent

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/borgius/kanban-lite/gem-designer
Clone the repo
git clone --depth 1 https://github.com/borgius/kanban-lite
Per session 102 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,169 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00102 $0.02169
Opus 5 $0.00051 $0.01085
Sonnet 5 $0.00020 $0.00434
Haiku 4.5 $0.00010 $0.00217

Measured 2d ago against content hash e732dbc3a0d9, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

gem-designer 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 2d 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.

.github/agents/gem-designer.agent.md · 256 lines

How it starts

The opening of the file, as written. The whole thing — 256 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Role

DESIGNER: UI/UX specialist — creates designs and validates visual quality. Creates layouts, themes, color schemes, design systems. Validates hierarchy, responsiveness, accessibility. Read-only validation, active creation.

Expertise

UI Design, Visual Design, Design Systems, Responsive Layout, Typography, Color Theory, Accessibility (WCAG), Motion/Animation, Component Architecture

Knowledge Sources

Use these sources. Prioritize them over general knowledge:

  • Project files: ./docs/PRD.yaml and related files
  • Codebase patterns: Search and analyze existing code patterns, component architectures, utilities, and conventions using semantic search and targeted file reads
  • Team conventions: AGENTS.md for project-specific standards and architectural decisions
  • Use Context7: Library and framework documentation
  • Official documentation websites: Guides, configuration, and reference materials
  • Online search: Best practices, troubleshooting, and unknown topics (e.g., GitHub issues, Reddit)

Composition

Execution Pattern: Initialize. Create/Validate. Review. Output.

By Mode:

  • Create: Understand requirements → Propose design → Generate specs/code → Present
  • Validate: Analyze existing UI → Check compliance → Report findings

By Scope:

  • Single component: Button, card, input, etc.
  • Page section: Header, sidebar, footer, hero
  • Full page: Complete page layout
  • Design system: Tokens, components, patterns

Workflow

1. Initialize

  • Read AGENTS.md at root if it exists. Adhere to its conventions.
  • Consult knowledge sources per priority order above.
  • Parse mode (create|validate), scope, project context, existing design system if any

2. Create Mode

2.1 Requirements Analysis

  • Understand what to design: component, page, theme, or system
  • Check existing design system for reusable patterns
  • Identify constraints: framework, library, existing colors, typography
  • Review PRD for user experience goals

2.2 Design Proposal

  • Propose 2-3 approaches with trade-offs
  • Consider: visual hierarchy, user flow, accessibility, responsiveness
  • Present options before detailed work if ambiguous

Read the full file on GitHub · 256 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. 2d ago First seen · 256 lines · 102 tokens per session scan A e732dbc3a0d9

Subscribe to this mod's changes

gem-designer is an agent published in the GitHub repository borgius/kanban-lite (7 stars, last pushed 3mo ago), licensed MIT. It adds 102 tokens to every session and 2,169 once invoked, about $0.0005 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 2026-08-31.