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Agent skill

Vellum Skill Authoring

by vellum-ai in vellum-ai/vellum-assistant

Author and review first-party Vellum skills in the repository.

MITAuto-check passedAgent Workflows

Install Vellum Skill Authoring

skills CLI
$ npx skills add vellum-ai/vellum-assistant --skill vellum-skill-authoring -a claude-code

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

GitHub CLI
$ gh skill install vellum-ai/vellum-assistant vellum-skill-authoring --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/vellum-ai/vellum-assistant.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.cursor/skills/vellum-skill-authoring .claude/skills/vellum-skill-authoring && 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
vellum-skill-authoring
GitHub stars
1.4k
Token cost
~470 tokens
SKILL.md length
224 words
Files
1
Skills in repo
108
Repo updated
First seen
Licence
MIT

At a glance

Author and review first-party Vellum skills in the repository.

  • Works in 5 steps: Verify tool input/output contracts are… → Check error handling and user-facing… → Confirm scripts can run in the skill… → …
  • Editing files under skills/
  • SKILL.md covers Scope, Core Constraints, SKILL.md Quality Bar and Tool And Script Review, plus 2 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Vellum Skill Authoring is an agent skill from vellum-ai/vellum-assistant. Author and review first-party Vellum skills in the repository. Use when editing files under skills/, assistant bundled skills, skill manifests, tool definitions, SKILL.md files, or first-party skill portability and isolation behavior.

Its SKILL.md is about 470 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, covering Skill authoring and Structured output and tool calling. The repository describes itself as: An AI Assistant that’s easy to setup, does your work 24/7, knows your preferences and gets better over time. The licence is MIT.

When your agent uses it

  • Editing files under skills/
  • Assistant bundled skills
  • Skill manifests
  • Tool definitions

Example prompts

  • “/vellum-skill-authoring”

Workflow steps

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

  1. Verify tool input/output contracts are explicit.
  2. Check error handling and user-facing messages.
  3. Confirm scripts can run in the skill process environment.
  4. Avoid direct imports across isolation boundaries.
  5. Add focused tests for parsing, contract handling, and failure cases.

What it can do on your machine

Read from SKILL.md and the folder at commit 33cc983. 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

Vellum Skill Authoring loads about 470 tokens when it runs. Until then it costs about 64 tokens; SKILL.md has 224 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~64
When it runs · the whole SKILL.md, loaded when a task matches
~470

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 vellum-ai/vellum-assistant at commit 33cc983, republished under its MIT licence (© vellum-ai). 224 words, ~470 tokens.

Download SKILL.mdSave it as .claude/skills/vellum-skill-authoring/SKILL.md (or your agent's skills folder).
name
vellum-skill-authoring
description
Author and review first-party Vellum skills in the repository. Use when editing files under skills/, assistant bundled skills, skill manifests, tool definitions, SKILL.md files, or first-party skill portability and isolation behavior.

Vellum Skill Authoring

Scope

Use this for Vellum runtime skills in skills/ and bundled assistant skills, not for Cursor Agent Skills under .cursor/skills/.

Core Constraints

  • First-party skills must be portable and isolated.
  • skills/ must not import from assistant/.
  • assistant/ must not import from skills/.
  • Prefer skill processes and supported contracts over new daemon tool registrations.
  • Avoid secrets, real personal data, and machine-specific paths in skill docs, tests, and fixtures.

SKILL.md Quality Bar

Skill instructions should be concise and operational:

  • State what the skill does and when to use it.
  • Prefer concrete steps over broad advice.
  • Keep user-facing terminology consistent.
  • Use generic examples only.
  • Avoid requiring hidden local state unless setup instructions create it.

Tool And Script Review

When a skill adds scripts or tools:

  1. Verify tool input/output contracts are explicit.
  2. Check error handling and user-facing messages.
  3. Confirm scripts can run in the skill process environment.
  4. Avoid direct imports across isolation boundaries.
  5. Add focused tests for parsing, contract handling, and failure cases.

Catalog And Packaging

When adding or renaming skills, check the relevant catalog, manifest, bundled registry, or packaging path used by the runtime. Do not assume a SKILL.md file alone makes the skill available to users.

Verification

Use focused tests around the changed skill, catalog entry, proxy bridge, or bundled registry. Add typecheck when contracts or generated manifests changed.

© vellum-ai, 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 .cursor/skills/vellum-skill-authoring of vellum-ai/vellum-assistant.

Open the folder on GitHubat commit 33cc983

Compare with similar skills

Vellum Skill Authoring 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.

Vellum Skill Authoring compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Vellum Skill Authoring this skillvellum-ai/vellum-assistant1.4k—~470Automated safety check: PassMIT
Skill CreatorAzure/azqr79689 repos~8.2kAutomated safety check: PassApache-2.0
Claude Code Skill Developer Guidediet103/claude-code-infrastructure-showcase10k11 repos~3.5kAutomated safety check: PassMIT
Darwin Skill Optimizeralchaincyf/darwin-skill6.2k1 repos~4.7kAutomated safety check: PassMIT
Claude Code Command Developmentanthropics/claude-plugins-official38k10 repos~4.8kAutomated safety check: PassApache-2.0
Claude Code Plugin Structureanthropics/claude-plugins-official38k10 repos~3.4kAutomated safety check: PassApache-2.0

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Categories

Questions about Vellum Skill Authoring

What does Vellum Skill Authoring do?

Author and review first-party Vellum skills in the repository. Vellum Skill Authoring is an agent skill from vellum-ai/vellum-assistant. Author and review first-party Vellum skills in the repository.

When should I use Vellum Skill Authoring?

Vellum Skill Authoring fits situations like: editing files under skills/; assistant bundled skills; skill manifests; tool definitions.

How do I install Vellum Skill Authoring in Claude Code?

Run `npx skills add vellum-ai/vellum-assistant --skill vellum-skill-authoring -a claude-code`. Or copy the skill folder (.cursor/skills/vellum-skill-authoring in vellum-ai/vellum-assistant) into .claude/skills/vellum-skill-authoring in your project. Claude Code loads it when a task matches its description.

How do I install Vellum Skill Authoring in Codex?

Run `npx skills add vellum-ai/vellum-assistant --skill vellum-skill-authoring -a codex`. Or copy the skill folder (.cursor/skills/vellum-skill-authoring in vellum-ai/vellum-assistant) into .agents/skills/vellum-skill-authoring in your project. Codex loads it when a task matches its description.

Can I use Vellum Skill Authoring 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 vellum-ai/vellum-assistant --skill vellum-skill-authoring -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/vellum-skill-authoring, .gemini/skills/vellum-skill-authoring, .github/skills/vellum-skill-authoring and .opencode/skills/vellum-skill-authoring in your project.

What does Vellum Skill Authoring need to run?

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

Does Vellum Skill Authoring 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 Vellum Skill Authoring 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 Vellum Skill Authoring use?

Vellum Skill Authoring 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 Vellum Skill Authoring use?

About 470 tokens (SKILL.md is roughly 1.9k 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 Vellum Skill Authoring?

Skills that share tags, products or a category with Vellum Skill Authoring: Skill Creator (Azure/azqr, 796 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, 38k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Vellum Skill Authoring?

vellum-ai (a GitHub organization) maintains it in vellum-ai/vellum-assistant, which has 1,408 GitHub stars. The repository holds 108 skills in this directory. The repository was last updated on October 9, 2026.

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