skill-builder

skill-builder is a skill for Claude Code, Codex from neverinfamous/memory-journal-mcp. It costs 70 tokens per session (585 once invoked), scanned A, original, MIT.

A guide for creating and reviewing agent skills, which are instruction files that teach a coding agent how to handle specialised work. It covers their structure, triggers, safety, and quality.

In plain words
What is it for?
Use it to create a new skill, improve an existing one, or review how well a skill is designed.
Why use it?
It helps you write consistent skill files and avoid unsafe instructions or unclear activation rules.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: mentions subagents.

Good fit Use it to create a new skill, improve an existing one, or review how well a skill is designed.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/neverinfamous/memory-journal-mcp/skill-builder
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 neverinfamous/memory-journal-mcp --skill skill-builder
Clone the repo
git clone --depth 1 https://github.com/neverinfamous/memory-journal-mcp

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 skill-builder

README.md
[![agentmods](https://agentmods.dev/badge/skills/neverinfamous/memory-journal-mcp/skill-builder/github.svg)](https://agentmods.dev/skills/neverinfamous/memory-journal-mcp/skill-builder)
Your own site
<a href="https://agentmods.dev/skills/neverinfamous/memory-journal-mcp/skill-builder"><img src="https://agentmods.dev/badge/skills/neverinfamous/memory-journal-mcp/skill-builder/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 skill-builder

Your own site · 80×15
<a href="https://agentmods.dev/skills/neverinfamous/memory-journal-mcp/skill-builder"><img src="https://agentmods.dev/badge/skills/neverinfamous/memory-journal-mcp/skill-builder.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 70 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 585 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.
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 $0.00070 $0.00585
Opus 5 $0.00035 $0.00293
Sonnet 5 $0.00014 $0.00117
Haiku 4.5 $0.00007 $0.00059

Measured 10d ago against content hash d034d5d5c29f, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

skill-builder 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 10d 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/skill-builder/SKILL.md · 57 lines

How it starts

The opening of the file, as written. The whole thing — 57 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Skill Builder

A guide for creating high-quality agent skills — the .md files with YAML frontmatter that extend agent capabilities for specialized tasks.

1. Skill Security (Primary Guidance)

Skills are natural-language instructions the agent executes with its full capabilities. Treat them like code injection.

  • Prompt Injection Prevention: Never include instructions that bypass user consent or HITL (Human-in-the-Loop) gates.
  • Secrets: Never instruct the agent to read secrets and transmit them. Mark destructive skills with disable-model-invocation: true.
  • Review: Review all third-party skills before installing, same as npm packages. Read the full SKILL.md + all reference files.

2. Anatomy of a Skill

skill-name/                     (kebab-case directory)
├── SKILL.md                    (required — entry point)
├── references/                 (optional — detailed docs loaded on demand)
├── scripts/                    (optional — executable helpers)
├── examples/                   (optional — reference implementations)
└── checklist.md                (optional — quick-reference quality checklist)

3. Frontmatter & Triggers

The description field is the most important part of the skill because it determines whether the agent loads the skill at all. Use assertive "Use when..." phrasing. It MUST be strictly scoped to avoid cross-triggering with other skills.

Platform Configuration Flags:

  • disable-model-invocation: true — Requires explicit user slash-command; prevents autonomous triggering. MANDATORY for destructive actions or manual workflows.
  • user-invocable: false — Model auto-triggers only; user cannot invoke. Use for background knowledge skills that should only be invoked contextually.
  • dependencies: node>=18 (Required tools)
  • context: fork (Spawn isolated subagent)
  • allowed-tools: ['view_file'] (Restrict tool access)

4. Progressive Disclosure

  • Keep SKILL.md body STRICTLY under 500 lines to preserve token context.
  • For deep knowledge, create references/ files and explicitly list them in SKILL.md.

Read the full file on GitHub · 57 lines

Files

What ships with it

2 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. 10d ago First seen · 57 lines · 70 tokens per session scan A d034d5d5c29f

Subscribe to this mod's changes

skill-builder is a skill published in the GitHub repository neverinfamous/memory-journal-mcp (20 stars, last pushed 1mo ago), licensed MIT. It adds 70 tokens to every session and 585 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 2026-08-30.

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