Callstack Agent Skills is a collection of instructions that gives AI coding assistants practical knowledge for building React Native applications. Developers use it for app development, performance, navigation, testing, CI, device automation, and migrations to React Native. The catalogue entries are the project's skills, rules, and instructions for compatible coding assistants.
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.
npx agentmods add skills/callstackincubator/agent-skills/validate-skillsnpx skills add callstackincubator/agent-skills --skill validate-skillsgit clone --depth 1 https://github.com/callstackincubator/agent-skillsWrote 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.
[](https://agentmods.dev/skills/callstackincubator/agent-skills/validate-skills)<a href="https://agentmods.dev/skills/callstackincubator/agent-skills/validate-skills"><img src="https://agentmods.dev/badge/skills/callstackincubator/agent-skills/validate-skills.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00029 | $0.00641 |
| Opus 5 | $0.00015 | $0.00320 |
| Sonnet 5 | $0.00006 | $0.00128 |
| Haiku 4.5 | $0.00003 | $0.00064 |
Grade A, and why
validate-skills 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 6d ago.
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.
How it starts
The opening of the file, as written. The whole thing — 65 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Validate Skills
Validate all skills in skills/ against the agentskills.io spec and Claude Code best practices.
Validation Checklist
For each skill directory, verify:
Spec Compliance (agentskills.io)
| Check | Rule |
|---|---|
name format |
1-64 chars, lowercase alphanumeric + hyphens, no leading/trailing/consecutive hyphens |
name matches directory |
Directory name must equal name field |
description length |
1-1024 characters, non-empty |
| Optional fields valid | license, metadata, compatibility if present |
Best Practices (Claude Code)
| Check | Rule |
|---|---|
| Description format | Third person, describes what + when to use |
| Body length | Under 500 lines |
| Loading is one-level deep | SKILL.md is the only progressive-disclosure entry point: every reference file must be reachable from SKILL.md. References may cross-link each other for navigation (see note below). |
| Links are markdown | Use [text](path) not bare filenames |
| No redundancy | Don't repeat description in body |
| Concise | Only add context Claude doesn't already have |
One-level-deep vs. cross-linking. The one-level-deep rule targets progressive-disclosure loading chains — a reference that can only be discovered by loading another reference first (
SKILL.md→a.md→b.md, whereb.mdis not linked fromSKILL.md). That is a defect: it hides content from the loader.It does not forbid navigational cross-links. Per AGENTS.md, reference files end with a "Related Skills" footer linking sibling references, and this is required. A cross-link is fine as long as both endpoints are also reachable directly from
SKILL.md. Only flag a reference that is reachable exclusively through another reference.
How to Run
-
Find all skill directories:
fd -t d -d 1 . skills/ -
For each skill, read
SKILL.mdand check against the rules above -
Report issues in this format:
## Validation Results ### skills/example-skill - [PASS] name format valid - [FAIL] name "example" doesn't match directory "example-skill" - [PASS] description length OK (156 chars)
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.
- 6d ago First seen · 65 lines · 29 tokens per session scan A cf2aec443ab2
validate-skills is a skill published in the GitHub repository callstackincubator/agent-skills (1,638 stars, last pushed 28d ago), licensed MIT. It adds 29 tokens to every session and 641 once invoked, about $0.0001 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 2026-08-30.
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