AI Engineering from Scratch is a free, open-source curriculum that teaches people to build AI systems through lessons and reusable artifacts such as prompts, skills, agents, and MCP servers. It is for learners who want practical foundations or want to create AI applications, and the catalogue skills support parts of that curriculum.
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 skills add rohitg00/ai-engineering-from-scratch --skill skill-catalog-buildergit clone --depth 1 https://github.com/rohitg00/ai-engineering-from-scratchWrote 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/rohitg00/ai-engineering-from-scratch/skill-catalog-builder)<a href="https://agentmods.dev/skills/rohitg00/ai-engineering-from-scratch/skill-catalog-builder"><img src="https://agentmods.dev/badge/skills/rohitg00/ai-engineering-from-scratch/skill-catalog-builder/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.
<a href="https://agentmods.dev/skills/rohitg00/ai-engineering-from-scratch/skill-catalog-builder"><img src="https://agentmods.dev/badge/skills/rohitg00/ai-engineering-from-scratch/skill-catalog-builder.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00023 | $0.00198 |
| Opus 5 | $0.00012 | $0.00099 |
| Sonnet 5 | $0.00005 | $0.00040 |
| Haiku 4.5 | $0.00002 | $0.00020 |
Grade A, and why
skill-catalog-builder 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.
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.
What it actually says
Skill catalog builder
Use this skill when an agent host needs deterministic discovery across more than one skill directory.
- Read
references/discovery-contract.md. - Review the example host policy in
assets/scope-policy.json; do not assume its order is universal. - Run
python3 scripts/build_catalog.py project=PATH user=PATHwith scopes listed from highest to lowest precedence. - Inspect the JSON
collisionsandomittedarrays before activating a skill. - Load only the selected SKILL.md body. Load a direct reference only when that body names it.
Never execute a bundled script during discovery. Never choose an equal-precedence duplicate by incidental filesystem order.
Return the catalog budget, selected entries, collision resolutions, and omissions.
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.
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.
- 9d ago First seen · 22 lines · 23 tokens per session scan A 85b778e99d31
skill-catalog-builder is a skill published in the GitHub repository rohitg00/ai-engineering-from-scratch (52,899 stars, last pushed yesterday), licensed MIT. It adds 23 tokens to every session and 198 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.
Other skills, from other repositories
skill-release-gate
A release-checking skill for evaluating whether an agent skill bundle is complete, safe, correctly triggered, and portable to its target host.
migration-review
A review workflow for database migration files, which change the structure or data rules of a database. It checks the requested migration files and the code needed to assess their compatibility.
skill-contract-reviewer
Validate an Agent Skill package and choose the right instruction, capability, or lifecycle primitive before implementation.
skill-invocation-router
A routing skill for deciding when an agent skill should activate and which request channel is allowed to activate it.
skill-catalog-builder
A catalogue-building skill for discovering agent skills from defined project and user locations while resolving duplicates and omissions by policy.
skill-safety-reviewer
A safety-review skill for examining proposed agent actions without running them. It checks filesystem access, commands, network use, secrets, and destructive operations against explicit sandbox rules.