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Agent skill

Double Check

by mrtooher in mrtooher/fable-mode

Automatic final verification pass on completed deliverables.

No licenceAuto-check passedAgent Workflows

Install Double Check

skills CLI
$ npx skills add mrtooher/fable-mode --skill double-check -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install mrtooher/fable-mode double-check --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/mrtooher/fable-mode.git skills-src && mkdir -p .claude/skills && cp -r skills-src/double-check .claude/skills/double-check && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
double-check
GitHub stars
870
Token cost
~1.9k tokens
SKILL.md length
1,024 words
Files
1
Skills in repo
7
Repo updated
First seen
Licence
None found

At a glance

Automatic final verification pass on completed deliverables.

  • Works in 6 steps: Extract claims and requirements → Detect the runtime, pick the mode → Verdicts — ternary, forced → …
  • The user says double check this
  • SKILL.md covers What it is and is not, When it runs, Skip conditions and Procedure, plus 1 more section
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Double Check is an agent skill from mrtooher/fable-mode. Automatic final verification pass on completed deliverables. Runs automatically at the end of every fable-mode run (fable-mode, fable-fable, fable-opus, fable-sonnet, fable-haiku) — those skills invoke it before delivery. Also triggers when the user says "double check this", "double-check", or wants the finished work re-checked without doing it themselves. Uses a panel of model-tier checker agents (Haiku for mechanical checks, Sonnet for logic/requirements, Opus to adjudicate disagreements) to verify the finished…

Its SKILL.md is about 1.9k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Agent Workflows. The repository describes itself as: A Claude skill that activates Fable-style agentic behavior: explicit multi-stage planning, sub-agent delegation, and self-verification.

When your agent uses it

  • The user says double check this
  • Wants the finished work re-checked without doing it themselves
  • Work still in progress
  • Never trigger on its own output (no recursion)

Example prompts

  • “double check this”
  • “double-check”
  • “/double-check”

Workflow steps

6 steps, taken from the step headings in SKILL.md.

  1. Extract claims and requirements
  2. Detect the runtime, pick the mode
  3. Verdicts — ternary, forced
  4. Check the synthesis seam
  5. Fix, then re-check
  6. Report

What it can do on your machine

Read from SKILL.md and the folder at commit a368f94. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Double Check loads about 1.9k tokens when it runs. Until then it costs about 177 tokens; SKILL.md has 1,024 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~177
When it runs · the whole SKILL.md, loaded when a task matches
~1.9k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

Without a licence we can't republish the file, so here is its outline and opening line. It has 1,024 words (~1,936 tokens).

“Automatic verification pass on a finished deliverable. The user should never have to re-check work themselves — this skill is that re-check.”

— opening of SKILL.md by mrtooher
name
double-check

Read the full SKILL.md on GitHub

Files

Just SKILL.md in double-check of mrtooher/fable-mode.

Open the folder on GitHubat commit a368f94

Compare with similar skills

Double Check next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Double Check compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Double Check this skillmrtooher/fable-mode870—~1.9kAutomated safety check: PassNone
MCP Server Builderanthropics/skills180k64 repos~2.3kAutomated safety check: PassApache-2.0
Hook Development for Claude Code Pluginsanthropics/claude-plugins-official38k11 repos~4.1kAutomated safety check: NotesApache-2.0
Using Superpowersfarm-fe/farm5.6k35 repos~1.4kAutomated safety check: PassMIT
Executing Plans Inlineobra/superpowers296k2 repos~5.1kAutomated safety check: PassMIT
Claude Code Agent Developmentanthropics/claude-plugins-official38k8 repos~2.8kAutomated safety check: PassApache-2.0

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    Explains how to write Claude Code plugin hooks, both prompt-based checks and bash commands, for events such as PreToolUse, Stop and SessionStart.

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Categories

Questions about Double Check

What does Double Check do?

Automatic final verification pass on completed deliverables. Double Check is an agent skill from mrtooher/fable-mode. Automatic final verification pass on completed deliverables.

When should I use Double Check?

Double Check fits situations like: the user says double check this; wants the finished work re-checked without doing it themselves; work still in progress; never trigger on its own output (no recursion).

How do I install Double Check in Claude Code?

Run `npx skills add mrtooher/fable-mode --skill double-check -a claude-code`. Or copy the skill folder (double-check in mrtooher/fable-mode) into .claude/skills/double-check in your project. Claude Code loads it when a task matches its description.

How do I install Double Check in Codex?

Run `npx skills add mrtooher/fable-mode --skill double-check -a codex`. Or copy the skill folder (double-check in mrtooher/fable-mode) into .agents/skills/double-check in your project. Codex loads it when a task matches its description.

Can I use Double Check in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add mrtooher/fable-mode --skill double-check -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/double-check, .gemini/skills/double-check, .github/skills/double-check and .opencode/skills/double-check in your project.

What does Double Check need to run?

SKILL.md names no scripts, command-line tools or credentials: Double Check is instructions for the agent only.

Does Double Check access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Double Check safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Double Check use?

No licence was found for Double Check or its repository. Without one, default copyright applies: ask the author before reusing or redistributing it.

How many tokens does Double Check use?

About 1.9k tokens (SKILL.md is roughly 7.7k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Double Check?

Skills that share tags, products or a category with Double Check: MCP Server Builder (anthropics/skills, 180k stars), Hook Development for Claude Code Plugins (anthropics/claude-plugins-official, 38k stars), Using Superpowers (farm-fe/farm, 5.6k stars) and Executing Plans Inline (obra/superpowers, 296k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Double Check?

mrtooher (a GitHub user) maintains it in mrtooher/fable-mode, which has 870 GitHub stars. The repository holds 7 skills in this directory. The repository was last updated on September 2, 2026.

Source: mrtooher/fable-mode on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.