learn

learn is a skill for Codex from nyaomaru/is-kit. It costs 38 tokens per session (976 once invoked), scanned A, original, MIT.

A workflow for extracting reusable lessons from significant TypeScript library work, such as API design, debugging, or compatibility discoveries.

In plain words
What is it for?
Use it after meaningful implementation or debugging work in the is-kit type-guard library to record design decisions, testing lessons, and runtime/type compatibility patterns.
Why use it?
It turns one-off problem solving into documented project knowledge that can guide future changes.

Skill for Codex

Written for Codex: installed under .codex/. Also seen: reads ~/.codex paths; mentions Codex.

Good fit Use it after meaningful implementation or debugging work in the is-kit type-guard library to record design decisions, testing lessons, and runtime/type compatibility patterns.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/nyaomaru/is-kit/learn
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.

Any agent
npx skills add nyaomaru/is-kit --skill learn
Clone the repo
git clone --depth 1 https://github.com/nyaomaru/is-kit

Made for: 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 learn

README.md
[![agentmods](https://agentmods.dev/badge/skills/nyaomaru/is-kit/learn/github.svg)](https://agentmods.dev/skills/nyaomaru/is-kit/learn)
Your own site
<a href="https://agentmods.dev/skills/nyaomaru/is-kit/learn"><img src="https://agentmods.dev/badge/skills/nyaomaru/is-kit/learn/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 learn

Your own site · 80×15
<a href="https://agentmods.dev/skills/nyaomaru/is-kit/learn"><img src="https://agentmods.dev/badge/skills/nyaomaru/is-kit/learn.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 38 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 976 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 pass 7 Sept 2026
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 $0.00038 $0.00976
Opus 5.5 $0.00015 $0.00390
Sonnet 5.5 $0.00008 $0.00195
Haiku 4.5 $0.00004 $0.00098

Measured 1mo ago against content hash db362ac51fc4, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

learn 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 1mo 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.

.codex/skills/learn/SKILL.md · 152 lines

How it starts

The opening of the file, as written. The whole thing — 152 lines — stays where its author put it; the contents beside it link to each section on GitHub.

/learn - Capture Reusable is-kit Patterns

Analyze the current session and capture reusable knowledge for this TypeScript type-guard library.

Auto-Activation Criteria

Consider auto-activating this skill when:

  1. A non-trivial bug was fixed in runtime guard behavior or type inference.
  2. A public API design decision was made and validated with tests.
  3. A tricky TypeScript modeling pattern was discovered.
  4. A runtime/type parity issue was diagnosed and resolved.
  5. The session produced reusable guidance about tests, docs, or release safety for this library.

Do not activate for:

  • trivial typo fixes
  • one-line doc wording changes
  • obvious refactors with no reusable lesson
  • patterns already documented in .codex/skills/learn/learned/

Manual Trigger

Run /learn after finishing a meaningful implementation, refactor, or debugging session in is-kit.

What To Extract

1. Public API Design Patterns

  • What API was added or changed?
  • Why was that shape chosen over alternatives?
  • What backward-compatibility constraint mattered?
  • How should similar future APIs be designed?

Project-relevant examples:

  • Distinguishing key-level optionality from value-level undefined.
  • Choosing a specialized combinator vs. a more generic abstraction.
  • Preserving existing semantics in a minor release while introducing a new helper.

2. Type Modeling Patterns

  • How were inference, narrowing, or overloads preserved?
  • What TypeScript limitation mattered?
  • What exact type shape or helper solved it?

Project-relevant examples:

  • Modeling struct schemas with required vs. optional keys.
  • Normalizing intersection-heavy inferred types for tsd.
  • Preserving literal narrowing without assertion casts.

3. Runtime Validation Patterns

  • What runtime behavior needed to match the type-level contract?
  • What edge cases mattered?
  • What implementation detail should future changes preserve?

Project-relevant examples:

  • Own-key checks vs. inherited property checks in struct.
  • Exact-mode semantics when optional keys are present or absent.
  • Composing schema markers with existing value guards.

Read the full file on GitHub · 152 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. 1mo ago First seen · 152 lines · 38 tokens per session scan A db362ac51fc4

Subscribe to this mod's changes

learn is a skill published in the GitHub repository nyaomaru/is-kit (134 stars, last pushed 3d ago), licensed MIT. It adds 38 tokens to every session and 976 once invoked, about $0.0002 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 2026-09-01.

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