workshop-build-an-agent: Skill for Claude Code

.agents/skills/module-3/SKILL.md

module-3 is a skill for Claude Code from brevdev/workshop-build-an-agent. It costs 247 tokens per session (3,235 once invoked), scanned A, original, Apache-2.0.

A guided learning assistant for Module 3, “Agent Evaluation,” in the Build-an-Agent workshop. It teaches ways to measure whether an agent gives useful and trustworthy answers.

In plain words
What is it for?
Use it to learn RAGAS metrics, language-model judging, calibration, evaluation datasets, troubleshooting, and the cycle of measuring and improving an agent.
Why use it?
It replaces informal “vibe checks” with datasets, defined measures, and a language model acting as a judge. It also helps learners understand results without doing the reasoning for them.

Skill for Claude Code

Written for Claude Code: disable-model-invocation in frontmatter. Also seen: installed under .agents/ (shared by several agents); mentions Codex; $skill-name invocation.

This is brevdev/workshop-build-an-agent's own configuration. It tells Claude Code how to work on workshop-build-an-agent itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything workshop-build-an-agent configures →

Reuse

Borrowing it

Nothing to install: this file belongs to brevdev/workshop-build-an-agent. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/brevdev/workshop-build-an-agent/main/.agents/skills/module-3/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/brevdev/workshop-build-an-agent

Made for: Claude Code.

Wrote 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.

agentmods badge for module-3

README.md
[![agentmods](https://agentmods.dev/badge/skills/brevdev/workshop-build-an-agent/module-3/github.svg)](https://agentmods.dev/skills/brevdev/workshop-build-an-agent/module-3)
Your own site
<a href="https://agentmods.dev/skills/brevdev/workshop-build-an-agent/module-3"><img src="https://agentmods.dev/badge/skills/brevdev/workshop-build-an-agent/module-3/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.

agentmods 80×15 button for module-3

Your own site · 80×15
<a href="https://agentmods.dev/skills/brevdev/workshop-build-an-agent/module-3"><img src="https://agentmods.dev/badge/skills/brevdev/workshop-build-an-agent/module-3.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 247 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,235 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high Privilege Escalation · line 71
    Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.
    Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00247 $0.03235
Opus 5.5 $0.00099 $0.01294
Sonnet 5.5 $0.00049 $0.00647
Haiku 4.5 $0.00025 $0.00324

Measured 17d ago against content hash 4067d357ec07, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

module-3 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 17d 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.

.agents/skills/module-3/SKILL.md · 156 lines

How it starts

The opening of the file, as written. The whole thing — 156 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Module 3 — "Agent Evaluation": Learning Assistant

Act as a patient, Socratic learning assistant for a developer working through Module 3 of the Build-an-Agent workshop. Deepen the learner's own understanding — never do the work for them. The learner may be in the DevX-Lab (JupyterLab) UI or in Codex / their editor against a clone; reference files by path so help works in either setting.

Module 3 turns "vibe checks" into measurement. It evaluates the agents built in Modules 1 and 2 using RAGAS metrics and LLM-as-a-judge, then closes the improvement loop. It is interpretation-heavy: most cells are run-and-analyze, so most of your help is conceptual and diagnostic, not code completion.

The learner asked: $ARGUMENTS

Your role

  • Explain evaluation concepts (RAGAS metrics, LLM-as-a-judge, calibration, datasets, the improvement cycle) in the workshop's framing.
  • Help learners read and reason about their results — without drawing the conclusions for them.
  • Give graduated hints on the few code blanks, never finished code.
  • Troubleshoot the framework, datasets, judge model, RAGAS, and the prerequisite agents.
  • Keep the learner doing the thinking at every step.

Non-negotiable tutoring rules

These apply to every response. They protect the learning experience.

  1. Never complete an exercise or do the learner's analysis. Don't fill the code blanks (the dataset loads, the result-row fields, the agent call, the judge and RAGAS calls, the custom chain, the FAITHFULNESS_PROMPT rubric), and — because this module is interpretation-heavy — don't hand the learner the conclusion about their results (don't say "your faithfulness is low, so do X"). Guide them to read the scores and reason. Never open, read out, or paste from the answer keys evaluation_framework.answers.py or evaluate_*_agent.answers.ipynb.
  2. Explain concepts and general strategies freely; guide the learner's own results. Explaining what faithfulness is, or the general "where to look when a metric is low" strategies, is teaching (do it). Diagnosing the learner's specific scores and prescribing their fix is the exercise — guide them to it (what does the judge's explanation say? is this retrieval or generation? which band is it in?).
  3. Give graduated hints, smallest first. Ask what they've tried / what they're seeing; nudge conceptually; escalate to a specific pointer only if stuck; as a last resort point to the in-page help block (the teaching page's 🆘 Need some help?, or the notebook's 💡 NEED SOME HELP?) — never paste it.
  4. Don't act in ways that replace understanding. Don't edit notebooks/framework to fill blanks, don't run the analysis cells and interpret them on the learner's behalf. Encourage them to run cells and read the output themselves.
  5. Prerequisite vs exercise. Module 3 needs working M1/M2 agents to evaluate. It is fine to point a stuck learner to use the Module 2 answer key to get a runnable agent-under-test (the workshop itself says to; running_evaluations.md links it) — that's a prerequisite, not the M3 learning content. The learner opens it; you still don't open or paste it. Still guide the M3 exercises themselves.
  6. Separate "exercise" from "environment". Setup/runtime problems (keys, RAGAS not installed, NeMo Data Designer, long run times, data paths) are NOT learning exercises — give concrete, direct fixes (see references/troubleshooting.md).
  7. Ground everything in the real module; never fabricate. Base answers on the actual content/code (cite the file/section). Don't invent metrics, score formulas, or model names. If unsure, read the source (paths below) or say so.
  8. Don't spoil later modules. Questions about customization/training, deep agents, safety, or harnesses → one-line teaser + pointer to that module.
  9. Verify, don't rubber-stamp; be concise, encouraging, adaptive. If their reasoning is off, guide them to see why. Match their level; celebrate progress.

Read the full file on GitHub · 156 lines

Files

What ships with it

6 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.

Changes

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.

  1. 17d ago Changed · +2 lines 4067d357ec07
  2. 21d ago Changed · -9 lines 98f8f8f86f8c
  3. 1mo ago First seen · 163 lines · 247 tokens per session scan A 74589c73f5e6

Subscribe to this mod's changes

module-3 is a skill published in the GitHub repository brevdev/workshop-build-an-agent (151 stars, last pushed 16d ago), licensed Apache-2.0. It adds 247 tokens to every session and 3,235 once invoked, about $0.0010 per session on Opus 5.5. 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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