ISO 24495 Plain Language Skills

Five Agent Skills that make an AI agent write in plain language, and help organisations implement it. They apply principles inspired by the ISO 24495 Plain language series to every user-facing response.

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

The core skill activates the legal and technical extensions automatically. It triggers iso-24495-2 for legal content and iso-24495-3 for technical content. The document design skill activates through its own description, or on request by name.

All skills exempt internal reasoning and preserve code blocks, commands, and logs untouched. 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 GaZmagik/iso-24495
/plugin install iso-24495-plain-language@iso-24495

Or from a local clone:

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

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."

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 affiliated with, endorsed by, or approved by the International Organization for Standardization (ISO). The skills contain original guidance inspired by the ISO 24495 series. They do not reproduce the text of any ISO standard.

Publication status: Part 1 published 2023, Part 2 August 2025, Part 3 May 2026. Parts 4 and 5 remain unpublished drafts (ISO/CD 24495-4 and ISO/WD 24495-5). Their skills are provisional guidance from public scope statements, to be revised when ISO publishes.

Conformance disclaimer. The full ISO 24495 texts are licensed and have not been consulted. These skills are built from public principles, published scopes, and common plain-language practice.

The principles derive from the International Plain Language Federation's freely published framework. Every quantitative rule here (sentence length, paragraph density, legalese, heading depth) is this project's own proxy. No rule is a clause of any standard.

Nothing this plugin produces is a statement of ISO conformance. No certification scheme exists for ISO 24495. "Aligned" in the skills means aligned with this project's interpretation, nothing more.

Background monitor (Claude Code)

The plugin ships a background monitor (monitors/monitors.json) for iso-24495-4 engagements. It stays silent unless the working directory contains .iso-24495-4/monitor.json naming a corpus directory:

{ "corpusDir": "docs" }

When configured, it re-audits changed documents and notifies the agent of rule-count deltas as they happen. Without a config it waits for one to appear and never exits on its own. The host therefore never raises a "task ended" notification.

Removing the config mid-session returns the monitor to the waiting state. It requires Bun and is Claude Code-specific; the skills themselves work without it.

Advisory markdown hook (Claude Code)

The plugin ships a PostToolUse hook (hooks/) that audits every markdown file Claude writes or edits. It uses the same rule engine as the Part 4 corpus audit. When a file carries violations, Claude receives one terse advisory line with per-rule counts.

A clean file produces nothing, and the hook never blocks a write.

To switch it off for a project, create .iso-24495-4/hooks.json containing:

{ "markdownAudit": false }

It requires Bun and is Claude Code-specific; the skills themselves work without it.

Why this project holds itself to these rules

This repository is both the tool and a user of the tool. Its hook audits every markdown edit, including this README. Its own audits have failed and forced rewrites; the changelog records them.

That is deliberate. A plain language project that exempts itself has no claim on anyone else. The Part 4 maturity audit runs against this repository first, and its findings are acted on here first.

Roadmap

All five skills, the output style, the background monitor, and the advisory markdown hook have shipped. What remains:

• 0.5.0: extend the advisory hook to plain-language checks on script comments (doc comments and docstrings, advisory only).
• When ISO publishes Part 4: revise the provisional iso-24495-4 skill against the published text. Its committee-draft text is not public, so the current maturity model is original guidance.
• When ISO publishes Part 5: revise the provisional iso-24495-5 skill against the published text.

Licence

MIT