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Agent skill

Harness Skill Creator

by QoderAI in QoderAI/better-harness

A skill your agent uses when bootstrapping or tightening the smallest harness-oriented skill from an existing repository, workflow, evaluation corpus, or harness-analysis chain.

MITAuto-check passedAgent Workflows

Install Harness Skill Creator

skills CLI
$ npx skills add QoderAI/better-harness --skill harness-skill-creator -a claude-code

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

GitHub CLI
$ gh skill install QoderAI/better-harness harness-skill-creator --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/QoderAI/better-harness.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/harness-skill-creator .claude/skills/harness-skill-creator && 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
harness-skill-creator
GitHub stars
2.4k
Token cost
~844 tokens
SKILL.md length
362 words
Files
2 (incl. references)
Skills in repo
11
Repo updated
First seen
Licence
MIT

At a glance

A skill your agent uses when bootstrapping or tightening the smallest harness-oriented skill from an existing repository, workflow, evaluation corpus, or harness-analysis chain.

  • Works in 7 steps: Resolve source, target, and host:… → Inspect the source chain before… → Load references/bootstrap-patterns.md… → …
  • Tightening the smallest harness-oriented skill from an existing repository
  • SKILL.md covers Workflow, Design Gates and Validation
  • Calls python3

What it does

Harness Skill Creator is an agent skill from QoderAI/better-harness. Use when bootstrapping or tightening the smallest harness-oriented skill from an existing repository, workflow, evaluation corpus, or harness-analysis chain. Trigger for meta skills, reusable harness workflows, Qoder/Codex plugin skill sets, skill blueprints, and harness-analysis-like skills that need evidence-backed references, validation gates, and qodercli forward-tests.

Its SKILL.md is about 840 tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files, including reference files (for example `references/bootstrap-patterns.md`).

It sits in Agent Workflows, covering Skill authoring. The repository describes itself as: An open-source Harness Engineering platform for coding agents—define harnesses as code, run controlled experiments, inspect evidence, and compare outcomes. Turn task evidence… The licence is MIT.

When your agent uses it

  • Tightening the smallest harness-oriented skill from an existing repository
  • Evaluation corpus
  • Harness-analysis chain
  • Reusable harness workflows

Example prompts

  • “/harness-skill-creator”

Requirements

  • Python 3

Workflow steps

7 steps, taken from the first numbered list in SKILL.md.

  1. Resolve source, target, and host: canonical skills//, .agents/skills/ wrapper, or both.
  2. Inspect the source chain before designing: entry SKILL.md, first-hop
  3. Load references/bootstrap-patterns.md after the first inventory. Use it to
  4. Draft the minimum viable skill map
  5. Initialize new canonical skills with the system skill-creator helper when
  6. Write the SKILL.md as a router. Put trigger conditions in frontmatter
  7. Validate locally, then forward-test. Treat qodercli output as model evidence;

What it can do on your machine

Read from SKILL.md and the folder at commit 34899f3. 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

    Shell commands in SKILL.md call:

    • python3

    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

Harness Skill Creator loads about 844 tokens when it runs, and up to ~1.7k if it reads all its reference files. Until then it costs about 100 tokens; SKILL.md has 362 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~100
When it runs · the whole SKILL.md, loaded when a task matches
~844
With references · SKILL.md plus every file in references/, read only if the agent opens them
~1.7k

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

The full file from QoderAI/better-harness at commit 34899f3, republished under its MIT licence (© QoderAI). 362 words, ~844 tokens.

Download SKILL.mdSave it as .claude/skills/harness-skill-creator/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.
name
harness-skill-creator
description
Use when bootstrapping or tightening the smallest harness-oriented skill from an existing repository, workflow, evaluation corpus, or harness-analysis chain. Trigger for meta skills, reusable harness workflows, Qoder/Codex plugin skill sets, skill blueprints, and harness-analysis-like skills that need evidence-backed references, validation gates, and qodercli forward-tests.

Harness Skill Creator

Create the smallest skill that makes another agent repeat one harness job with evidence, validation, and clear ownership.

Workflow

  1. Resolve source, target, and host: canonical skills/<name>/, .agents/skills/ wrapper, or both.
  2. Inspect the source chain before designing: entry SKILL.md, first-hop references, scripts, validators, templates, specs, tests, plugin manifests, and any real smoke evidence.
  3. Load references/bootstrap-patterns.md after the first inventory. Use it to extract patterns, not product-specific rules.
  4. Draft the minimum viable skill map:
    • skill name and trigger sentence
    • one job the skill owns
    • files to create under skills/<skill-name>/, usually SKILL.md plus one reference
    • evidence boundary and validation commands
    • forward-test prompt and pass/fail gates
  5. Initialize new canonical skills with the system skill-creator helper when available. Add scripts/ only for stable repeated automation; keep ad-hoc evaluation prompts out of runtime scripts.
  6. Write the SKILL.md as a router. Put trigger conditions in frontmatter description, keep the body short, and route detailed rules to first-hop references.
  7. Validate locally, then forward-test. Treat qodercli output as model evidence; local validators and file inspection decide pass/fail.
Show full SKILL.md (184 more words)Show less

Design Gates

  • Prefer one skill over a stage tree until the target process proves multiple reusable stages.
  • Copy ownership shape, not product names, branch policy, private commands, or source-specific team routing.
  • Keep .agents/skills/ as a wrapper or mirror when the workflow is shared by the plugin; canonical judgment belongs under root skills/.
  • Do not add install, network, server, migration, or dependency-changing commands unless the user requested them and source evidence supports them.
  • Prefer portable Node/Python validators or target-owned commands. Do not default generated validation gates to Unix-only grep/find checks.
  • In attachment-only or no-tools forward-tests, never emit tool-call markup, shell probes, or inspection plans; return the skill map with status: "insufficient-evidence" when needed.
  • Forward-test files is a string array of skills/<skill-name>/... paths, not objects.
  • If the generated skill cannot pass quick_validate.py <skill-dir>, do not describe it as usable.
  • After any forward-test, verify git status or file inventory for every repo the model was allowed to read or write.

Validation

Run the narrowest useful gates for the created skill:

bash
python3 <skill-creator-root>/scripts/quick_validate.py <skill-dir>
qodercli --cwd <neutral-dir> --plugin-dir <harness-root> -p "<forward-test prompt>"
qodercli plugin validate <harness-root>

Reject missing frontmatter, stale placeholders, broken links, unsupported commands, source-only assumptions, pseudo tool calls, or broad reports.

© QoderAI, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 1 other file (references) in .agents/skills/harness-skill-creator of QoderAI/better-harness.

  • SKILL.md
  • references/bootstrap-patterns.md

Open the folder on GitHubat commit 34899f3

Compare with similar skills

Harness Skill Creator 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.

Harness Skill Creator compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Harness Skill Creator this skillQoderAI/better-harness2.4k—~844Automated safety check: PassMIT
Skill CreatorAzure/azqr79489 repos~8.2kAutomated safety check: PassApache-2.0
Claude Code Skill Developer Guidediet103/claude-code-infrastructure-showcase10k10 repos~3.5kAutomated safety check: PassMIT
Darwin Skill Optimizeralchaincyf/darwin-skill6.2k1 repos~4.7kAutomated safety check: PassMIT
Claude Code Command Developmentanthropics/claude-plugins-official37k10 repos~4.8kAutomated safety check: PassApache-2.0
Claude Code Plugin Structureanthropics/claude-plugins-official37k10 repos~3.4kAutomated safety check: PassApache-2.0

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Categories

Questions about Harness Skill Creator

What does Harness Skill Creator do?

A skill your agent uses when bootstrapping or tightening the smallest harness-oriented skill from an existing repository, workflow, evaluation corpus, or harness-analysis chain. Harness Skill Creator is an agent skill from QoderAI/better-harness. Use when bootstrapping or tightening the smallest harness-oriented skill from an existing repository, workflow, evaluation corpus, or harness-analysis chain.

When should I use Harness Skill Creator?

Harness Skill Creator fits situations like: tightening the smallest harness-oriented skill from an existing repository; evaluation corpus; harness-analysis chain; reusable harness workflows.

How do I install Harness Skill Creator in Claude Code?

Run `npx skills add QoderAI/better-harness --skill harness-skill-creator -a claude-code`. Or copy the skill folder (.agents/skills/harness-skill-creator in QoderAI/better-harness) into .claude/skills/harness-skill-creator in your project. Claude Code loads it when a task matches its description.

How do I install Harness Skill Creator in Codex?

Run `npx skills add QoderAI/better-harness --skill harness-skill-creator -a codex`. Or copy the skill folder (.agents/skills/harness-skill-creator in QoderAI/better-harness) into .agents/skills/harness-skill-creator in your project. Codex loads it when a task matches its description.

Can I use Harness Skill Creator 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 QoderAI/better-harness --skill harness-skill-creator -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/harness-skill-creator, .gemini/skills/harness-skill-creator, .github/skills/harness-skill-creator and .opencode/skills/harness-skill-creator in your project.

What does Harness Skill Creator need to run?

Going by SKILL.md and its folder, Harness Skill Creator needs the command-line tools its instructions call (python3). Our summary lists: Python 3.

Does Harness Skill Creator 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 Harness Skill Creator 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 Harness Skill Creator use?

Harness Skill Creator is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Harness Skill Creator use?

About 844 tokens (SKILL.md is roughly 3.4k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 902 tokens, read only when the agent opens those files.

What are the alternatives to Harness Skill Creator?

Skills that share tags, products or a category with Harness Skill Creator: Skill Creator (Azure/azqr, 794 stars), Claude Code Skill Developer Guide (diet103/claude-code-infrastructure-showcase, 10k stars), Darwin Skill Optimizer (alchaincyf/darwin-skill, 6.2k stars) and Claude Code Command Development (anthropics/claude-plugins-official, 37k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Harness Skill Creator?

QoderAI (a GitHub organization) maintains it in QoderAI/better-harness, which has 2,363 GitHub stars. The repository holds 11 skills in this directory. The repository was last updated on September 28, 2026.

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