lessons

lessons is a skill for Claude Code, Codex from xtone/ai_development_tools. It costs 113 tokens per session (2,731 once invoked), scanned A, original, no licence file.

A skill for managing the “Lessons Learned” section of a CLAUDE.md file, a project instruction file for Claude.

In plain words
What is it for?
Use it to add lessons with `/lessons`, review existing rules with `/lessons review`, or update CLAUDE.md based on session findings.
Why use it?
It provides a structured place to record and review lessons from fixes, failures, and discoveries.

Skill for Claude CodeCodex

Part of the common-development plugin — 6 skills shipped together

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/xtone/ai_development_tools/lessons-md-manager
Any agent
npx skills add xtone/ai_development_tools --skill lessons-md-manager
Clone the repo
git clone --depth 1 https://github.com/xtone/ai_development_tools

Made for: Claude Code, Codex.

Or install common-development, the plugin that ships this one along with the rest of its 6 skills.

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 lessons

README.md
[![agentmods](https://agentmods.dev/badge/skills/xtone/ai_development_tools/lessons-md-manager.svg)](https://agentmods.dev/skills/xtone/ai_development_tools/lessons-md-manager)
Your own site
<a href="https://agentmods.dev/skills/xtone/ai_development_tools/lessons-md-manager"><img src="https://agentmods.dev/badge/skills/xtone/ai_development_tools/lessons-md-manager.svg" alt="Measured on agentmods" height="20"></a>
Per session 113 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,731 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin unknown 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 $0.00113 $0.02731
Opus 5 $0.00056 $0.01366
Sonnet 5 $0.00023 $0.00546
Haiku 4.5 $0.00011 $0.00273

Measured 3d ago against content hash 4002405ccb8b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

lessons 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 3d 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.

common_development/skills/lessons-md-manager/SKILL.md · 247 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

Files

What ships with it

1 file 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. 3d ago First seen · 247 lines · 113 tokens per session scan A 4002405ccb8b

Subscribe to this mod's changes

lessons is a skill published in the GitHub repository xtone/ai_development_tools (3 stars, last pushed 9d ago), with no licence file. It adds 113 tokens to every session and 2,731 once invoked, about $0.0006 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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