Ship one skill that agents load on at least 90% of 20 should-trigger prompts and at most 10% of 20 should-not prompts, with SKILL.md under 500 lines (about 5,000 tokens), passing skills-ref validate, and installable in 2 different agents with one command.
Recommended stack
- Agent Skills specification (agentskills.io) - File format: SKILL.md frontmatter plus scripts/, references/, assets/. One open format read by many agents, with progressive disclosure so only name and description load until needed.
- skills-ref 0.1 (installs the
agentskillsCLI) - Validator. Checks frontmatter and naming rules (lowercase, hyphens, matches directory, max 64 chars). - skills CLI 1.7 (npx skills) - Install from a git repo or local path. Installs into 75+ agents from GitHub, GitLab, any git URL, or a folder.
- A small trigger/quality eval script - Measures trigger rate and task quality with and without the skill. Description wording decides loading, and only a test shows if it works.
Build steps
- Pick one repeatable task agents get wrong without guidance; write down 3 examples of the task done well and 3 common failures.
- Create
<name>/SKILL.mdwhere name is lowercase with single hyphens, at most 64 chars, and matches the folder. - Write the description (max 1024 chars) as a trigger: what it does plus "Use when ..." with the words users actually type.
- Write the body: numbered steps, an input/output example, edge cases. Move long reference material to references/*.md (one level deep) and deterministic work to scripts/ with clear error messages.
- Keep it agent-agnostic: no agent-specific tool names or paths; add the compatibility field only if it needs specific system packages or network access.
- Validate with
agentskills validate ./<name>(frompip install skills-ref; the spec page calls it skills-ref validate). - Install non-interactively with
npx skills add ./<name> -a <agent> -a <agent> -yinto 2 agents (set DISABLE_TELEMETRY=1 to opt out of the CLI's install telemetry), run 20 should-trigger and 20 should-not prompts in each, count a trigger when the agent's transcript or tool log shows it read/SKILL.md, record trigger rates, and compare task quality with and without the skill on 5 tasks. - Push to a public repo and document the install line
npx skills add https://github.com/<owner>/<repo>/tree/main/skills/<name>.
Watch out for
- Vague descriptions ("Helps with PDFs") rarely trigger. Name the file types, verbs, and phrases users say.
- Putting everything in SKILL.md burns context on every load. Split into references and scripts.
- Uppercase letters, a double hyphen, or a folder-name mismatch fail validation and some installers.
- Scripts that assume a specific OS shell or a global tool without saying so fail silently in other agents.
Definition of done
agentskills validate ./<name>prints 'Valid skill' and exits 0.- Trigger test shows at least 90% on positives and at most 10% on negatives in both agents.
- A fresh machine installs it with one npx skills command.
- With-skill output beats without-skill output on at least 4 of 5 tasks.