skill-evolver

skill-evolver is a skill for Claude Code, Codex from Stijnman/grok-custom-skills. It costs 37 tokens per session (408 once invoked), scanned A, original, MIT.

A controlled editing tool for rewriting and improving an agent skill while keeping a versioned backup of its instructions.

In plain words
What is it for?
It helps prepare reviewable rewrites, explain expected benefits and risks, apply approved changes, and test the result.
Why use it?
It helps improve a skill while preserving a way to review the changes and return to the earlier version if needed.

Skill for Claude CodeCodex

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

Good fit It helps prepare reviewable rewrites, explain expected benefits and risks, apply approved changes, and test the result.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/stijnman/grok-custom-skills/skill-evolver
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.

Any agent
npx skills add Stijnman/grok-custom-skills --skill skill-evolver
Clone the repo
git clone --depth 1 https://github.com/Stijnman/grok-custom-skills

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 skill-evolver

README.md
[![agentmods](https://agentmods.dev/badge/skills/stijnman/grok-custom-skills/skill-evolver/github.svg)](https://agentmods.dev/skills/stijnman/grok-custom-skills/skill-evolver)
Your own site
<a href="https://agentmods.dev/skills/stijnman/grok-custom-skills/skill-evolver"><img src="https://agentmods.dev/badge/skills/stijnman/grok-custom-skills/skill-evolver/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 skill-evolver

Your own site · 80×15
<a href="https://agentmods.dev/skills/stijnman/grok-custom-skills/skill-evolver"><img src="https://agentmods.dev/badge/skills/stijnman/grok-custom-skills/skill-evolver.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 37 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 408 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.
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 $0.00037 $0.00408
Opus 5 $0.00018 $0.00204
Sonnet 5 $0.00007 $0.00082
Haiku 4.5 $0.00004 $0.00041

Measured 9d ago against content hash 4f303e67e9fe, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

skill-evolver 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 9d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/validate_skill.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

.grok/skills/skill-evolver/SKILL.md · 51 lines

What it actually says

Skill Evolver

When to Use

  • User says evolve skill or task matches this capability
  • User says upgrade SKILL.md or task matches this capability
  • User says improve skill file or task matches this capability

Workflow

  1. Create a local versioned backup of the target SKILL.md and read references/evolution-guide.md for the rubric.
  2. Prepare a reviewable rewrite diff that identifies the affected sections, expected benefits, and rollback path.
  3. Obtain explicit user approval before applying, saving, committing, publishing, or otherwise persisting the rewrite.
  4. After approval, apply the rewrite and validate it with hyper-skill-tester. Present any rollback option for approval rather than restoring automatically.

References

Read references/evolution-guide.md when setup, backends, or rubric details are needed.

Integrations

  • skill-evolution-engine
  • hyper-skill-tester
  • natural-language-to-skill

Error Handling

Failure Response
Broken frontmatter Preserve the draft, show the local backup and rollback diff, and wait for user approval before restoring.

Gotchas

  • Read references/evolution-guide.md before major rewrites.

Example

Input: User request matching triggers above. Output: Structured result per workflow with integrations invoked as needed.

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 9d ago First seen · 51 lines · 37 tokens per session scan A 4f303e67e9fe

Subscribe to this mod's changes

skill-evolver is a skill published in the GitHub repository Stijnman/grok-custom-skills (9 stars, last pushed yesterday), licensed MIT. It adds 37 tokens to every session and 408 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 2026-09-03.

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