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-contract-reviewergit 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-contract-reviewer)<a href="https://agentmods.dev/skills/rohitg00/ai-engineering-from-scratch/skill-contract-reviewer"><img src="https://agentmods.dev/badge/skills/rohitg00/ai-engineering-from-scratch/skill-contract-reviewer/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-contract-reviewer"><img src="https://agentmods.dev/badge/skills/rohitg00/ai-engineering-from-scratch/skill-contract-reviewer.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 | $0.00024 | $0.00381 |
| Opus 5 | $0.00012 | $0.00191 |
| Sonnet 5 | $0.00005 | $0.00076 |
| Haiku 4.5 | $0.00002 | $0.00038 |
Grade A, and why
skill-contract-reviewer 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 11d 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 contract reviewer
Use this skill when a workflow is about to become a reusable agent artifact.
- Set
SKILL_ROOTto the absolute directory containing this installedSKILL.md. Do not assume the process working directory is the bundle. - Set
TARGET_ROOTto the absolute original workspace working directory and resolve the proposed skill directory under that root. - Read
$SKILL_ROOT/references/contract.mdand validate the portableSKILL.mdidentity fields. - Read
$SKILL_ROOT/references/decision-model.mdand separate repository context, reusable method, external capability, lifecycle timing, deterministic logic, and isolated delegation. - Before execution, show the exact resolved argument vector. Run
python3 "$SKILL_ROOT/scripts/check_skill.py" "$TARGET_SKILL", whereTARGET_SKILLis the absolute proposed skill directory underTARGET_ROOT. - Inspect the JSON report. Fix every error before discussing host-specific extensions.
- Compare the proposed artifact with
$SKILL_ROOT/assets/task-shapes.jsonand return the smallest composable set of primitives.
Do not claim that a runtime extension is part of the portable contract. Do not treat a valid skill as permission to run scripts or access tools.
Return the validation report, the selected primitives, and one sentence explaining each selection. Include execution evidence with the resolved script path, resolved target path, cwd, exact argv, and exit code. If the host cannot expose one of those observations, mark it unverified instead of inventing it.
What ships with it
4 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.
- 11d ago First seen · 38 lines · 24 tokens per session scan A 84345705cb49
skill-contract-reviewer is a skill published in the GitHub repository rohitg00/ai-engineering-from-scratch (54,035 stars, last pushed 3d ago), licensed MIT. It adds 24 tokens to every session and 381 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.
skill-contract-reviewer
Validate an Agent Skill package and choose the right instruction, capability, or lifecycle primitive before implementation.
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-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.