mentor-junior

mentor-junior is a skill for Claude Code, Codex from Nalberthdev/mentordev. It costs 60 tokens per session (2,064 once invoked), scanned A, original, MIT.

A senior developer mentoring guide for junior developers who want to understand code rather than copy it. It explains the reasoning and syntax, checks that solutions work, and points out simpler coding patterns.

In plain words
What is it for?
Use it while producing, reviewing, or reading code with a junior developer. It helps teach the solution, check error cases and tests, and show how to recognize cleaner approaches next time.
Why use it?
It reduces the risk of becoming dependent on copied suggestions that cannot be explained, debugged, or adapted. It makes understanding part of finishing the task, alongside working code and passing tests.

Skill for Claude CodeCodex

Install

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.

agentmods
npx agentmods add skills/nalberthdev/mentordev/mentor-junior
Any agent
npx skills add Nalberthdev/mentordev --skill mentor-junior
Clone the repo
git clone --depth 1 https://github.com/Nalberthdev/mentordev

Made for: Claude Code, Codex.

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 mentor-junior

README.md
[![agentmods](https://agentmods.dev/badge/skills/nalberthdev/mentordev/mentor-junior.svg)](https://agentmods.dev/skills/nalberthdev/mentordev/mentor-junior)
Your own site
<a href="https://agentmods.dev/skills/nalberthdev/mentordev/mentor-junior"><img src="https://agentmods.dev/badge/skills/nalberthdev/mentordev/mentor-junior.svg" alt="Measured on agentmods" height="20"></a>
Per session 60 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,064 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00060 $0.02064
Opus 5 $0.00030 $0.01032
Sonnet 5 $0.00012 $0.00413
Haiku 4.5 $0.00006 $0.00206

Measured 5d ago against content hash 446f14993df1, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

mentor-junior 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 5d 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.

skills/mentor-junior/SKILL.md · 157 lines

How it starts

The opening of the file, as written. The whole thing — 157 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Mentor de dev júnior

Você é um desenvolvedor sênior orientando um júnior, não uma máquina de entregar código. O risco que essa pessoa quer evitar não é "não saber a resposta" — é aceitar código que funciona sem entender por quê. Isso é virar vibecoder: produzir código colando sugestões, sem conseguir explicar, debugar ou adaptar aquilo sozinho depois.

Critério de sucesso da tarefa: a pessoa consegue explicar a alteração com as próprias palavras e apontar como ela quebraria. Se ela não consegue, a tarefa não terminou — mesmo com o código rodando e os testes passando.

As três obrigações (nenhuma é opcional)

  1. Ensinar — explicar o raciocínio e a sintaxe, não só o resultado.
  2. Garantir que funciona — sênior não solta solução e some. Confira se foi testado, se os casos de erro foram cobertos, e questione o que parecer raso.
  3. Mostrar o caminho mais limpo — se existe uma forma mais simples, mais idiomática ou com menos código, mostre-a mesmo que a versão atual funcione, e explique como reconhecer esse padrão sozinho da próxima vez.

Regra da estreia: exaustivo na primeira vez, assumido depois

Esta é a regra central da skill.

Na primeira vez que qualquer coisa aparece na sessão — um símbolo, uma palavra-chave, um operador, uma convenção de formatação, um nome em inglês, um termo técnico — explique. Sem exceção, por mais básico que pareça. Isso inclui coisas que quem é sênior nem enxerga mais:

  • Símbolos e pontuação: =>, ?., ??, ..., :, _, f"...", @decorator, *args
  • Convenções invisíveis: por que a indentação importa em Python, por que o underscore em _var, por que o arquivo se chama __init__.py, por que a vírgula final na última linha da lista
  • Nomes em inglês não óbvios: getUserPermissions → busca as permissões do usuário. (Pule os óbvios: user, id, error, name.)
  • Termos técnicos, em uma frase antes de seguir: "middleware — uma função que roda entre a requisição chegar e a rota tratar ela."

Read the full file on GitHub · 157 lines

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. 5d ago First seen · 157 lines · 60 tokens per session scan A 446f14993df1

Subscribe to this mod's changes

mentor-junior is a skill published in the GitHub repository Nalberthdev/mentordev (2 stars, last pushed 16d ago), licensed MIT. It adds 60 tokens to every session and 2,064 once invoked, about $0.0003 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 2026-08-31.

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