lai-gen-language-skill

lai-gen-language-skill is a skill for Claude Code from eclipse-langium/langium-ai. It costs 33 tokens per session (2,426 once invoked), scanned A, original, MIT.

A guide for creating a reusable instruction file that teaches an AI agent a specific Langium-based language. Langium is a framework for building custom programming languages and developer tools.

In plain words
What is it for?
Use it when documenting a custom language’s grammar, meaning, common patterns, limitations, and mistakes for developers or AI agents.
Why use it?
It turns project details about the language into standalone guidance, so an agent can work with the language without reading the original project every time.

Skill for Claude Code

Written for Claude Code: user-invocable in frontmatter. Also seen: reads .claude/ paths; mentions CLAUDE.md; mentions Claude Code.

Good fit Use it when documenting a custom language’s grammar, meaning, common patterns, limitations, and mistakes for developers or AI agents.

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Install with agentmods
npx agentmods add skills/eclipse-langium/langium-ai/lai-gen-language-skill
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 eclipse-langium/langium-ai --skill lai-gen-language-skill
Clone the repo
git clone --depth 1 https://github.com/eclipse-langium/langium-ai

Made for: Claude Code.

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 lai-gen-language-skill

README.md
[![agentmods](https://agentmods.dev/badge/skills/eclipse-langium/langium-ai/lai-gen-language-skill/github.svg)](https://agentmods.dev/skills/eclipse-langium/langium-ai/lai-gen-language-skill)
Your own site
<a href="https://agentmods.dev/skills/eclipse-langium/langium-ai/lai-gen-language-skill"><img src="https://agentmods.dev/badge/skills/eclipse-langium/langium-ai/lai-gen-language-skill/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 lai-gen-language-skill

Your own site · 80×15
<a href="https://agentmods.dev/skills/eclipse-langium/langium-ai/lai-gen-language-skill"><img src="https://agentmods.dev/badge/skills/eclipse-langium/langium-ai/lai-gen-language-skill.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 33 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,426 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 warn 7 Sept 2026
SkillSpector: 2 findings, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium Agent Snooping · line 44
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
  • medium Agent Snooping · line 60
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
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 $0.00033 $0.02426
Opus 5 $0.00016 $0.01213
Sonnet 5 $0.00007 $0.00485
Haiku 4.5 $0.00003 $0.00243

Measured 11d ago against content hash c6f669beddce, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

lai-gen-language-skill 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 11d 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/lai-gen-language-skill/SKILL.md · 225 lines

How it starts

The opening of the file, as written. The whole thing — 225 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Generate Language Skill

This guide instructs an agent on how to generate a comprehensive, standalone skill document (a markdown file) for working with a specific Langium-based DSL. The output skill should give any agent or developer a deep understanding of the target language — its syntax, semantics, use cases, patterns, and pitfalls — without requiring access to the original project sources at runtime.

You may also use the lai and langium skills to achieve a better understanding of langium-ai and the Langium-based DSL in question that we wish to generate a skill for.

When to Use

  • After a descriptor and system prompt have been generated and refined (lai gen descriptor, lai gen sysprompt)
  • When you want to produce a reusable knowledge artifact (e.g., a SKILL.md or CLAUDE.md section) that teaches an agent how to work with your DSL
  • When onboarding new developers or agents to an existing DSL project
  • When creating documentation that goes beyond a system prompt — covering not just "how to generate code" but "how to think in this language"

Inputs

Gather these from the project before generating the skill:

  1. Language descriptor (language.descriptor.yml) — the structured YAML descriptor produced by lai gen descriptor
  2. Grammar file (.langium) — the full grammar definition
  3. Example files — all example programs referenced in the descriptor
  4. Validator source — the custom validator implementation (if any)
  5. Scope provider source — the custom scoping implementation (if any)
  6. Other custom services — linker, name provider, type provider, etc.
  7. Test files — existing tests that demonstrate expected behavior and edge cases
  8. Documentation — any referenced docs (README, language guides, etc.)
  9. Existing system prompt — the generated system prompt, which already contains a curated view of the language

Output Location

The generated skill must be placed in the project's existing skills directory, following the standard skill folder convention:

Read the full file on GitHub · 225 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. 11d ago First seen · 225 lines · 33 tokens per session scan A c6f669beddce

Subscribe to this mod's changes

lai-gen-language-skill is a skill published in the GitHub repository eclipse-langium/langium-ai (30 stars, last pushed 14d ago), licensed MIT. It adds 33 tokens to every session and 2,426 once invoked, about $0.0002 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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