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Agent skill

Aspens Agent Template Customizer

by aspenkit in aspenkit/aspens

Injects a project's own skills and AGENTS.md content into generic bundled agent template files, adding a tech-stack line and real conventions without touching an agent's core logic.

MITAuto-check passedAgent Workflows

Install Aspens Agent Template Customizer

skills CLI
$ npx skills add aspenkit/aspens --skill agent-customization -a claude-code

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

GitHub CLI
$ gh skill install aspenkit/aspens agent-customization --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/aspenkit/aspens.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/agent-customization .claude/skills/agent-customization && 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
agent-customization
GitHub stars
102
Token cost
~898 tokens
SKILL.md length
410 words
Files
1
Skills in repo
12
Repo updated
First seen
Licence
MIT

At a glance

Injects a project's own skills and AGENTS.md content into generic bundled agent template files, adding a tech-stack line and real conventions without touching an agent's core logic.

  • Making bundled generic agent templates aware of a specific project's stack
  • SKILL.md covers Domain purpose, Business rules / invariants, Non-obvious behaviors and Critical files (purpose, not…, plus 1 more section
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
  • Re-rolling an upgrade across agents that were customized under an older version

What it does

The skill backs the aspens customize agents command, which pulls a repository's skills and AGENTS.md as ground truth and asks the Claude CLI to add a tech-stack line, three to five project conventions and real commands into each generic agent file under .claude/agents/. It is a Claude-only feature that refuses to run on a Codex-only repository, and it requires a base skill to already exist, failing with a clear error that tells the user to run the init command first if one is missing.

The customizing LLM call is invoked with read-only tools, Read, Glob and Grep, so it never edits or writes files itself; a separate write step restricted to paths under .claude/ performs the actual file output. Frontmatter handling is split between the prompt and the code: the prompt preserves existing YAML frontmatter verbatim, and a post-processing step then injects a skills line referencing the base skill into every returned file. A reset flag controls whether an agent that already declares its own skills list is left alone or has that list forcibly overwritten, which is used to roll out upgrades to agents customized under an older version.

When your agent uses it

  • Making bundled generic agent templates aware of a specific project's stack
  • Re-rolling an upgrade across agents that were customized under an older version
  • Diagnosing why agent customization refused to run on a repository

Example prompts

  • “Run aspens customize agents and show me what conventions it added to each agent.”
  • “Reset the skills line on all customized agents to pick up the new base skill.”
  • “Why does agent customization say the base skill is required here?”

Requirements

  • The aspens CLI
  • A Claude Code target with .claude/skills/base/SKILL.md present

What it can do on your machine

Read from SKILL.md and the folder at commit 8dde826. 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

Aspens Agent Template Customizer loads about 898 tokens when it runs. Until then it costs about 30 tokens; SKILL.md has 410 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~30
When it runs · the whole SKILL.md, loaded when a task matches
~898

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 aspenkit/aspens at commit 8dde826, republished under its MIT licence (© aspenkit). 410 words, ~898 tokens.

Download SKILL.mdSave it as .claude/skills/agent-customization/SKILL.md (or your agent's skills folder).
name
agent-customization
description
LLM-powered injection of project context into installed agent templates via `aspens customize agents`
triggers.files
src/commands/customize.js, src/prompts/customize-agents.md
triggers.keywords
customize, agents, subagent, agent customization

You are working on agent customization — the feature that reads a project's skills and AGENTS.md, then uses Claude CLI to inject project-specific context into generic agent files in .claude/agents/.

Domain purpose

aspens customize agents makes generic, bundled agent templates project-aware. It pulls the repo's skills + AGENTS.md as ground truth and asks Claude to add a tech-stack line, 3-5 project conventions, and real commands into each agent — without touching the agent's core logic.

Business rules / invariants

  • Claude-only feature. Throws CliError for Codex-only repos (config.targets === ['codex']). Codex CLI has no agent concept.
  • Base skill is required. Pre-flight throws CliError("Run 'aspens doc init' first — base skill is required for agent context.") if .agents/skills/base/SKILL.md is missing.
  • Skills (.claude/skills/**) are the single source of truth for project context. The prompt must not invent other context directories.
  • Read-only tools only. Claude is invoked with allowedTools: ['Read', 'Glob', 'Grep'] — no edits/writes from the LLM itself.
  • Output paths restricted to .claude/. parseFileOutput() rejects anything else; writeSkillFiles(..., { force: true }) does the actual write.

Non-obvious behaviors

  • Frontmatter preservation is split across LLM + code. The prompt instructs Claude to preserve YAML frontmatter verbatim (including NOT adding a skills: line). Then maybeInjectBaseSkill() post-processes each returned file to add skills: [base] into the frontmatter — this keeps agents valid even when installed via aspens add agent without a prior doc init.
  • --reset semantics: without --reset, agents that already declare skills: are left alone; with --reset, any existing skills: line is overwritten to skills: [base]. Used to roll out v0.8 upgrades to previously-customized agents.
  • ## Project context block is verbatim-preserved by the prompt — it carries conditional read instructions for code-map / domain skills.
  • AGENTS.md is truncated at 3000 chars in gatherProjectContext(); skills are passed in full.
  • Agent discovery: findAgents() recursively walks .claude/agents/, extracts name: via regex, falls back to filename if missing.
  • Default timeout 300s via resolveTimeout(options.timeout, 300); ASPENS_TIMEOUT env var honored with warning on invalid value.
Show full SKILL.md (100 more words)Show less

Critical files (purpose, not inventory)

  • src/commands/customize.js — orchestrator: preflight, agent discovery, context gathering, per-agent Claude calls, post-LLM skills: [base] injection, write.
  • src/prompts/customize-agents.md — system prompt; enforces frontmatter + ## Project context preservation and bans file-inventory / hub-ranking output.

Critical Rules

  • Never let the LLM emit a skills: line — the prompt forbids it and the code adds it. If you change one, change both.
  • Never weaken path sanitization — only .claude/ paths may be written.
  • Never duplicate file-inventory or hub-ranking output in customized agents — the graph hook supplies that dynamically.
  • Do not bypass the base-skill preflight — agents without base context regress to generic behavior.

Last Updated: 2026-05-11

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

Files

Just SKILL.md in .agents/skills/agent-customization of aspenkit/aspens.

Open the folder on GitHubat commit 8dde826

Compare with similar skills

Aspens Agent Template Customizer 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.

Aspens Agent Template Customizer compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Aspens Agent Template Customizer this skillaspenkit/aspens102—~898Automated safety check: PassMIT
Using Agent Skillsaddyosmani/agent-skills102k4 repos~2.4kAutomated safety check: PassMIT
Task Observerrebelytics/one-skill-to-rule-them-all3.2k1 repos~12kAutomated safety check: PassCC-BY-4.0
Rules Distillationaffaan-m/ECC274k2 repos~2.3kAutomated safety check: PassMIT
Birdview Skills Compatibility AuditQiuner/birdview715—~794Automated safety check: PassMIT
Context Routing Auditwithkynam/vibecode-pro-max-kit1.1k—~1.2kAutomated safety check: PassMIT

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Categories

Questions about Aspens Agent Template Customizer

What does Aspens Agent Template Customizer do?

Injects a project's own skills and AGENTS.md content into generic bundled agent template files, adding a tech-stack line and real conventions without touching an agent's core logic. claude/agents/. It is a Claude-only feature that refuses to run on a Codex-only repository, and it requires a base skill to already exist, failing with a clear error that tells the user to run the init command first if one is missing.

When should I use Aspens Agent Template Customizer?

Aspens Agent Template Customizer fits situations like: making bundled generic agent templates aware of a specific project's stack; re-rolling an upgrade across agents that were customized under an older version; diagnosing why agent customization refused to run on a repository.

How do I install Aspens Agent Template Customizer in Claude Code?

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

How do I install Aspens Agent Template Customizer in Codex?

Run `npx skills add aspenkit/aspens --skill agent-customization -a codex`. Or copy the skill folder (.agents/skills/agent-customization in aspenkit/aspens) into .agents/skills/agent-customization in your project. Codex loads it when a task matches its description.

Can I use Aspens Agent Template Customizer 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 aspenkit/aspens --skill agent-customization -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/agent-customization, .gemini/skills/agent-customization, .github/skills/agent-customization and .opencode/skills/agent-customization in your project.

What does Aspens Agent Template Customizer need to run?

SKILL.md names no scripts, command-line tools or credentials: Aspens Agent Template Customizer is instructions for the agent only. Our summary lists: The aspens CLI; A Claude Code target with .claude/skills/base/SKILL.md present.

Does Aspens Agent Template Customizer 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 Aspens Agent Template Customizer 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 Aspens Agent Template Customizer use?

Aspens Agent Template Customizer 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 Aspens Agent Template Customizer use?

About 898 tokens (SKILL.md is roughly 3.6k 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 Aspens Agent Template Customizer?

Skills that share tags, products or a category with Aspens Agent Template Customizer: Using Agent Skills (addyosmani/agent-skills, 102k stars), Task Observer (rebelytics/one-skill-to-rule-them-all, 3.2k stars), Rules Distillation (affaan-m/ECC, 274k stars) and Birdview Skills Compatibility Audit (Qiuner/birdview, 715 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Aspens Agent Template Customizer?

aspenkit (a GitHub organization) maintains it in aspenkit/aspens, which has 102 GitHub stars. The repository holds 12 skills in this directory. The repository was last updated on September 12, 2026.

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