fk-thumbnail-guide

A set of rules and templates for designing YouTube thumbnails, including limits for text, faces, colors, composition, and lighting.

In plain words
What is it for?
Use it to guide thumbnail prompts for reactions, before-and-after images, transformations, reveals, and other video concepts.
Why use it?
It removes guesswork when creating thumbnails and helps avoid common layout problems, such as placing text where YouTube controls cover it.

Command for Claude Code

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 commands/crisng95/flowkit/fk-thumbnail-guide
Clone the repo
git clone --depth 1 https://github.com/crisng95/flowkit

Made for: Claude Code.

Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,030 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 $0.00000 $0.01030
Opus 5 $0.00000 $0.00515
Sonnet 5 $0.00000 $0.00206
Haiku 4.5 $0.00000 $0.00103

Measured 2d ago against content hash 1658f9359659, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

fk-thumbnail-guide 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.

.claude/commands/fk-thumbnail-guide.md · 86 lines

How it starts

The opening of the file, as written. The whole thing — 86 lines — stays where its author put it; the contents beside it link to each section on GitHub.

YouTube Thumbnail Guide — Hook-Worthy Design Rules

Required Elements

Element Rule
Text 0-3 words max. Bold thick sans-serif. Yellow/white on dark. Upper half only. Never bottom-right (YouTube overlays duration there)
Face 30-50% of frame. Extreme emotion: shock, anger, fear, determination. Direct eye contact. Never neutral/calm
Colors Red + Blue, Yellow + Purple, Orange + Teal. High saturation. No pastels, no gray, no muted tones
Composition ONE focal point. Subject 40-60% of frame. Blurred/simple background. Rule of thirds
Lighting Dramatic — rim light, golden hour, high-contrast shadows. Never flat/even

6 Thumbnail Formulas

Formula 1: Reaction Face (Best for drama/reveals)

  • Tight face crop 40-50% of frame, extreme emotion
  • 1-3 power words upper corner
  • Subject reacting to something partially visible
  • Prompt pattern: Extreme close-up of [CHARACTER] face, [EMOTION], [BACKGROUND ELEMENT partially visible], bold vivid colors, dramatic rim lighting

Formula 2: Before/After (Best for transformations)

  • Split screen: state A left, state B right
  • Clear dividing line
  • Prompt pattern: Split composition, left side shows [STATE A], right side shows [STATE B], dramatic contrast

Formula 3: Contrast/Clash (Best for military/underdog)

  • Two visually incompatible things: massive vs small, hero vs overwhelming enemy
  • High visual tension
  • Prompt pattern: [SMALL HERO] facing [MASSIVE THREAT], extreme scale contrast, cinematic wide angle

Formula 4: Mystery/Reveal (Best for secrets/twists)

  • Key element partially hidden or out of frame
  • Text: "?", "Nobody expected..."
  • Prompt pattern: [SUBJECT] looking at something dramatic off-screen, [EMOTION], mysterious lighting, partial reveal

Formula 5: Stakes Frame (Best for military/survival)

  • Single character against impossible odds
  • Environment communicates extreme pressure
  • Prompt pattern: [CHARACTER] surrounded/outnumbered by [THREAT], tension, dramatic environment showing scale of danger

Read the full file on GitHub · 86 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 · 86 lines · 0 tokens per session scan A 1658f9359659

Subscribe to this mod's changes

fk-thumbnail-guide is a command published in the GitHub repository crisng95/flowkit (620 stars, last pushed 14d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 1,030 tokens. 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.