ISO 24495 Plain Language Skills

Seven Agent Skills that support plain language writing, document audits, code, and organisational implementation. They apply principles inspired by the ISO 24495 Plain language series.

The skills are plain SKILL.md files with agent-neutral wording. Any tool that reads the Agent Skills format can use them.

This repository also packages them as a Claude Code plugin with an ISO 24495 output style (output-styles/iso-24495.md). Select the style with /output-style to hold every response to the core rules without relying on skill activation.

Skills

Skill	Scope
iso-24495-1	Core principles. Governs all user-facing output: no filler preambles, short sentences and paragraphs, active voice, scannable structure, concrete instructions.
iso-24495-2	Legal writing. Extends the core skill for contracts, licences, and compliance text: standardised modal verbs, no legalese, named actors, structured conditional clauses, defined terms, cross-references that name what they point at, stable clause identifiers, a summary layer over the operative text, and section names a reader can navigate by.
iso-24495-3	Science and technical writing. Extends the core skill for documentation, architecture, and code review: progressive disclosure, exact file citations, defined acronyms, text alternatives for diagrams, and the stages placed inside the document levels of iso-24495-5.
iso-24495-4	Organisational implementation (provisional). A task skill for plain language gap analysis in organisations: a process-artefact sweep, a corpus audit, a five-dimension maturity model with deterministic scoring, and an append-only audit trend. Ships TypeScript tooling run with Bun (bun test covered). Based on the unpublished ISO/CD 24495-4 committee draft.
iso-24495-5	Document design (provisional). Extends the core skill for structuring complex documents: an opening block, visual hierarchy, navigation aids, layered detail, comparisons, consistent signalling, and a signpost for the reader who wanted a different document. Ships a decision record, a runbook and a design document template. Based on the unpublished ISO/WD 24495-5 working draft.
iso-24495-code	Plain language in code. Applies the principles to what a person reads in source: the order units appear in, their names, what comments say, and what an error tells the reader who hits it. Measured to change how Claude structures a file, at no cost to correctness.
iso-24495-text-audit	User-invoked text audit. Checks a selected .md, .markdown, or .txt file or directory. Reports mechanical findings with locations, without deciding validity or compliance.

The core skill activates the relevant writing skills automatically. It triggers iso-24495-2 for legal content, iso-24495-3 for technical content, and iso-24495-5 for complex documents. A legal document always pairs with iso-24495-5, and a technical one does whenever its output is a document. The text audit never activates automatically.

All skills exempt internal reasoning. The writing skills preserve code blocks, commands, and logs untouched; iso-24495-code is the exception, because governing code is its subject. Technical and legal accuracy always supersede formatting rules.

Installation (Claude Code)

Add this repository as a plugin marketplace, then install the plugin:

/plugin marketplace add https://github.com/GaZmagik/iso-24495.git
/plugin install iso-24495-plain-language@iso-24495

Use the full HTTPS address as shown. The short owner/repo form makes some Claude Code versions clone over SSH, which fails without GitHub SSH keys.

Or from a local clone:

/plugin marketplace add ./path/to/this/repo
/plugin install iso-24495-plain-language@iso-24495

Installation (Codex CLI)

Codex reads the same marketplace manifest, so the plugin installs from the same address:

codex plugin marketplace add https://github.com/GaZmagik/iso-24495.git
codex plugin add iso-24495-plain-language@iso-24495

Or from a local clone, where . is the repository root:

codex plugin marketplace add .
codex plugin add iso-24495-plain-language@iso-24495

Every skill carries agents/openai.yaml, which gives Codex its display name, its short description, and the prompt Codex offers for it. Invoke a skill by name, as in $iso-24495-1, or ask for it in words.

Codex has no output style, so the same rules are a skill there: iso-24495-style holds the output style word for word, and a test keeps the two identical. It lives in codex-skills/ rather than skills/, because Claude Code scans skills/ and would otherwise offer a skill its output style already covers. Codex reads both directories, named in .codex-plugin/plugin.json.

Name the skill in your AGENTS.md to apply it to every response:

Apply `iso-24495-style` to every response.

Put that in your project's AGENTS.md or in ~/.codex/AGENTS.md. An AGENTS.md inside a plugin is ignored, so a plugin cannot apply itself.

Usage

Once installed, the agent loads the skills when their descriptions match the task. To apply one explicitly, ask for it by name, for example: "Apply iso-24495-2 to this licence text."

Invoke iso-24495-text-audit directly and supply one file or directory. The skill reads only that path and leaves every change to the user:

/iso-24495-plain-language:iso-24495-text-audit docs/policy.md

To enforce the core skill on every response, add a line to your agent's instruction file (CLAUDE.md, AGENTS.md, or equivalent):

- ALWAYS activate and adhere to the `iso-24495-1` Plain Language skill across all responses

For agents without a plugin system, copy the skills/ subdirectories into wherever the tool discovers skills.

Disclaimer

This unofficial project is not affil